As an answer, or perhaps multiple answers, to this question, should be a hierarchy of the tags used on the main site.
Here's a bare list, excluding synonyms, with * meaning the tag has been incorporated into an answer:
* adultery
* agriculture
* aishes-chayil
* am-yisrael-jewish-nation
* animals
* anti-semitism
* arachin-tractate
* ashkenazi
* astronomy
* bal-tashchit-waste
* bal-tosif-no-adding
* balak
* bamidbar-numbers-book-of
* basar-bechalav
* bava-kamma
* bava-metzia
* bechor-firstborn
* bechukosai
* behaalotcha-parsha
* behar
* beit-din-court
* bentching
* beshalach
* bigdei-kehunah
* bikkurim-first-fruits
* birchas-kohanim
* bitul-batel-null
* blessing
* blood
* bo
* book-of-ruth
* borrowing
* bowing-kneeling
* breslov
* brit-milah
* calendar
* candle-lighting
* chabad
* chagim-holidays
* chalav-yisrael-jewishmilk
* challah-shabbat-bread
* chametz-leaven
* chanuka
* chasidut-hasidism
* chassidic-rebbe
* chol-hamoed
* christianity
* chukas
* chulin-tractate
* churban-destruction
* conditional-stipulation
* cooking-bishul
* dairy
* daniel-book-of
* derech-eretz-manners
* devarim-deuteronomy-book
* devorim
* dina-dmalchusa-dina
* edim-witnesses
* eggs
* egypt
* ekev
* eliyahu-hanavi
* elul
* eruv-chatzerot
* estates-inheritance
* evening-night
* ezekiel--the-book
* family-members
* fast-days
* fish
* food
* four-cups-wine
* four-parshiot
* gebrochts
* gentiles
* gerut-conversion
* gezel-stealing
* gid-hanashe
* gid-hanashe
* golus-exile
* grapes-wine
* haftarah
* halacha
* hallel
* hamantashen
* har-sinai
* hashkafah-philosophy
* havdalah
* holocaust-shoah
* honey
* hosea--book-of
* hoshana-rabbah
* idolatry
* inebriation
* isaiah-yeshaya-the-book
* islam
* job-iyov-book-of
* joshua--book-of
* kashering-kosherization
* kashrut-kosher
* ki-tavo
* ki-teitzei
* kiddush
* kiddush-cup
* kiddush-levanah
* kilayim-forbidden-mixture
* kitniyos-semigrain-legume
* kohelet
* kohen-priest
* korban
* lag-ba-omer
* lamentations-eicha
* lashon-hara-slander
* leket-shichecha-peah
* lending-interest-ribbis
* levites-leviyim
* lo-yilbash
* lulav-etrog-arba-minim
* maakeh
* maariv
* maaser-tithes
* mamzer
* marror-bitter-herbs
* maseches-bechoros
* maseches-beitza
* maseches-eruvin
* maseches-gitin
* maseches-kiddushin
* maseches-kinim
* maseches-menachos
* maseches-sanhedrin
* maseches-shabbos
* maseches-shkalim
* maseches-taanis
* masechet-berachot
* masechet-makkot
* masecheth-avodah-zarah
* masei
* mattos
* matzah
* meat
* megillat-esther
* melacha-creative-work
* melachim-kings-book-of
* menora-chanukia
* messiah
* mezuzah
* middos-character-traits
* miketz
* mikvah-ritual-bath
* mincha-afternoon-prayer
* minhag
* mir
* mishlei
* mishloach-manot
* mishna
* mishpatim
* mitzvah
* months
* motzei-shabbos
* mourning-aveilus
* muktzeh
* murder
* musaf
* nachum-book-of
* navi-prophets
* nedarim-vows
* negia
* netilat-yadayim-washing
* nevua-prophecy
* nidah
* nine-days
* nissan
* nitzavim
* non-jewish-holidays
* nozir
* nusach-ari
* nusach-ashkenaz
* nusach-edot-hammizrach
* nusach-sefard
* nuschaot
* oil
* orla-revai
* parashas-emor
* parashas-kedoshim
* parashas-shemos
* parashas-shoftim
* parashas-yisro
* parashat-bereishit
* parashat-chaye-sara
* parashat-ki-tisa
* parashat-lech-lecha
* parashat-metzora
* parashat-noach
* parashat-shelach
* parashat-shemini
* parashat-tazria
* parashat-teruma
* parashat-toldot
* parashat-tzav
* parashat-vayeishev
* parsha-torah-portion
* parshat-korach
* parshat-nasso
* parshat-zachor
* passover
* passover-seder-hagada
* pentateuch-chumash
* pidyon-haben
* pikuachnefesh-danger-life
* pinchas
* plagues-makkos
* prayer-book
* pregnancy-birth
* purim
* rabbis
* repentance-teshuvah
* rosh-chodesh-new-month
* rosh-hashanah-new-year
* safrus
* samuel-shmuel-book-of
* sanhedrin-high-court
* sefer-torah
* sefirat-ha-omer
* selichot
* selling-mechirat-chametz
* separating-challah
* sephardi-mizrachi-eastern
* shabbat
* shabbat-songs
* shacharis-morning-prayer
* shatnez
* shaving
* shavuos
* shehecheyanu
* sheker-false
* shema
* shemona-esrei
* shemos-sacred-names
* shemot-exodus
* shiluach-haken
* shir-hashirim
* shiurim-measurements
* shmini-atzeres
* shmita
* shofar
* shoftim--book-of
* simchat-torah
* slaughter-shochet-shecht
* slave-serve-eved-avadim
* sorcery-magic-kishuf
* stringency-chumrah
* sukkah
* sukkot
* summer
* tachanun
* tallit-gadol
* tallit-katan
* talmud-bavli
* talmud-gemara
* talmud-yerushalmi
* tanach
* tattoo
* tattoo
* techeles
* tefilin
* tefilla
* tehilim-psalms
* tetzaveh
* tevilas-keilim-dipping
* theology
* three-weeks
* time
* time-zone
* tisha-bav
* torah-reading
* torah-service
* torah-study
* tractate-sotah
* transactions
* trees
* trei-asar
* tu-bishvat
* tumah-ritual-impurity
* tzedakah-charity
* tzitzis
* va-eira
* vaeschanan
* vayakhel
* vayechi
* vayeitzei
* vayera
* vayigash
* vayishlach
* yashan-chadash
* yemenite-temani
* yeshiva-school
* yetziat-mitzrayim
* yichud-seclusion
* yirmiyahu--book-of
* yizkor
* yom-haatzmaut
* yom-hashoah
* yom-hazikaron
* yom-kippur
* yom-shabbaton
* yom-tov
* yonah-jonah-book-of
* zemanim
* zimun
15th-of-av
7-mitzvos-of-noach
70-nations
acronyms
adon-olam
adult-learning
agada-stories-legends
age
aguna
ahavat-hashem
ahavat-yisrael
alacrity-for-mitzvot
aleph-bet-letters
aliya-laaretz
allegory-mashal
am-haaretz
amalek
amen
apocrypha
appliances
arabic
aramaic
archaeology
architecture-design
arizal
ark-aron-kodesh
army-military-war
artscroll
aseres-hadibros
aseres-yemei-teshuva
asher-yatzer
astrology
authorship
avot-patriarch-fathers
ayin-hara-evil-eye
baal-teshuva
baby-infant
babylonian-exile
bar-bas-bat-mitzvah
bar-kochva
bathroom
beard
bein-adam-lachavero
beis-hamikdash
binding-of-isaac
biography
birchos-hatorah
black-hats
book-banning
books-generally
borer-separating
borrer
bother-tircha
bread
bribery
brisk
bugs
business
calculation
capital-punishment
cemetery
cemetery-grave
chagiga-tractate
chagim-holidaysshiv
chatzitzah
chatzos
chazzan-prayer-leader
cherem
chesed-kindness
children-parenting
chilul-kidush-hashem
chinuch-education
choleh-sick
choshen-mishpat-civil-law
choson-kallah
chovel-umazik
chutz-laaretz
cities
city-of-refuge
cleaning
clothing
code-cipher-cryptogram
color
commentaries
commentary
communities
concubinage
contradiction-stira
creation
criminal-procedure
current-events
curse
daf-yomi
dance
darchei-emori
daytime
death
death-penalty
demography
derabanan
dictionary
dirty
disposal
divorce
drush
eating
eisav
electricity
emes-truth-honesty
employment
emunah
enemies
english
eretz-yisrael
erev-shabbat
eruv-tavshilin
ervah
eschatology
esther
ethiopian-beta-israel
etymology
even-haezer
evil-resha
evolution
explanation-rec
ezra-nechemya
faith-bitachon-emunah
fire-burning
fool
free-will-bechira
friendship
fruits
funeral-burial-levaya
gabbai
games-toys
gan-eden
gehinnom
gemach
gematria-numerology
genealogy
genevas-hadas
geography
geonim
gifts
glass
golden-calf-egel
grammar-dikduk
gravestone-inscription
haazinu
hachana-prep-for-weekday
hachnasat-orchim-guests
hagbah
hagomel
hair
hair-covering
hakaras-hatov
halacha-theory
halachah-theory
haman
hamotzi-beracha
handedness
handicap-disabled-impair
haredim
hashgacha-pratit
hashkafah
hasidic-story
health-safety-shmira
hearing
heaven
hebrew
hechsher-certification
hefsek-interruption
hellenism
heresy
heterodox
hillel
hishtadlut-effort
historical-figures
history
holy-objects
home-house
honors
hotel
hotzaa-carrying-reshuyot
humor
ikarim
illustrations
imahot-matriarch-mothers
inspection
intellectual-property
intent-accident-purposely
internet
invalid-pasul
jewelry
jewish-books
jewish-date-series
kabbalah
kabbalah-maasis
kabbalat-hatorah
kabbalat-shabbat
kaddish
kaparot
karet
kashruth
kavana-concentration
kavod
kedusha-holiness
kedusha-prayer
kerovim-close-relatives
ketubah
kibbud-av-veim-honoring
kiddush-hachodesh
kiddushin-eirusin
king-david
king-solomon
kippa-yarmulka
kiruv-outreach
kissing
kneading-lash
kol-isha
kol-mikadesh
korbanos-ketores-prayers
kotel-western-wall
kusim
language
lashes-malkot
latid-lavo-future
legal-documents
leil-shabbat
leniencies
lifnei-iver
lighting
liquor-beer
lo-bashamayim-hi
lomdus
loshon-hara
loud-quiet
mabul
machlokes
maftir
maharal
mail
makeh-befatish
malach-angel
malachi-book-of
malchut-royalty
mankind
marit-ayin
marriage
martyr
maseches-beitzah
maseches-kelayim
maseches-makos
maseches-moed-katan
masechet-kutim
masechet-yevamot
masechtot-ketanot
mathematics
meal-seudah
mechitza-partition
medicine
meditation
mekach-taut
melacha-erasing
melchizedek
memory
men-male
menorah
meraked
mesirath-nefesh
mesorah-tradition
mezonot-beracha
mi-yodeya-series
middos-chasidus
midrash
migdal-bavel
mincha-meal-offering
minor-katan-child
minyan
miracle
miriam
mishkan-tabernacle
mishnah-berurah
misnaged
mistakes
mizbeach
mon-manna
money
moon
moshe-feinstein
moshe-rabbeinu
motzi-yedei-chovato
music
mussar-ethics
mysticism-kabbalah
myths
nail-cutting
names
natural-phenomenon
niddah
noach-noah-the-man
noachide-laws
non-food
non-kosher-species
number
olam-haba-world-to-come
oneg-shabbat
opening-the-ark
oral-law
oral-torah
organizatons
orthodox
ouhistory
outer-space
parashanut-torah-comment
parashat-reeh
parashat-vayechi
parashat-vayikra
parashat-vezot-habracha
parnassah-livelihood
parshanut-theory
parshanut-torah-comment
parshat-shelach
parties-celebrations
parts-of-the-body
payot-sideburns
peace-shalom
performance-entertainment
petur-exemption
peyot
phone
pictures
pidyon-shvuyim-prisoners
pirke-avot-ethicsof
pirkei-drebbi-eliezer
plant
politics-government
popular-culture
posek-psak-decisor-ruling
possessed
poultry
priorities
product-recommendation
pronunciation
proof-of-torah
prophecies
protective-casing
provenance
psych-mentalhealth
public-policy
publications
purim-torah-in-jest
quotations
rabbeinu-tam
rabbeinu-yonah
rabbi-akiva-ben-yosef
rambam
ramban
ramchal
rashi
rationalism
real-estate
rebuke-tochacha
recording
religious-articles
resurrection-of-the-dead
reward-punishment
riddle
rif-rabbi-isaac-alfasi
rishonim
russian
sadducees
safek
sages-chazal
salt
samson-raphael-hirsch
science
seasons
seder-taharot
seder-zeraim
see-sight-vision-blind
segulah
semicha
sexuality
shabbetai-tzvi
shaul
sheidim-demons
sheva-brachos
shevatim-12-tribes
shidduchim-dating
shimshon-samson
shlichus-agency
shmuel--the-man
shomrim-bailees
shoteh-mental-incompetent
shovavim-tat
showering-bathing
shulchan-aruch
simchah-joy-happiness
sin
site-policy
sitting-shiva
siyum
size
sleep
smell
snow
social-convention
soloveitchik
song-poetry
soul
sources-mekorot
speech-talking
speeches-addresses
spelling-variants
sport-athletics
stackexchange
standing-sitting
star-of-david
statistics
suicide
swear-oath
swimming
symbols-symbology
synagogue
taamei-mitzvot-reasons
tahanun
tannaim
targum-translation
technology
tefilat-haderech
text
tikkun-chatzot
time-limited-commandments
tobacco-cig-smoking
torts-damages
tosfot
tractate-kerisus
tractate-megillah
tractate-nedarim
translation
transliteration
travel
trop-cantillation
trust-neemanut
tu-bshevat
tur
twins
tying-knots-kosheir
tzaar-baalei-chayyim
tzaddikim
tzaraas-negaim
tzibur-community
tznius-modesty
upsherin
vegetables
vehicles-transportation
vidui-confession
viduy-confession
vilna-gaon
vilna-shas
violence
voting
vowels-nekudot
water
weather
wedding
weights-and-measures
women
words
writing-printing
yael
yahrtzeit
yerushalayim-jerusalem
yibum-chalitza-levirate
yiddish
yigdal
yisro--the-man
yom-yerushalayim
yonah-jonah--the-man
yoreh-deah
yosef
yotzrot
yovel
zealotry
zecharia-book-of
zevulun
zionism