Last updated: December 11, 2023
Feel free to post links to other mod hosting sites in the discussion thread as long as it's "safe for work". I will then place your suggestion into the post with the suitable category in the main thread ("Mod hosting sites").
Table of Contents
General mod hosting sites
Bethesda Games
Mod author's websites
Miscellaneous mod hosting sites
General mod hosting sites
Nexus Mods
Mod DB
GameBanana
Steam Workshop
Based Mods
GameFront
Modding Haven
RPGHQ
Bethesda Games
Bethesda.net Mods (only Skyrim and Fallout 4)
AFK Mods (The Elder Scrolls and Fallout series)
TES Alliance (mostly Skyrim and Oblivion)
Emma's Elder Scrolls Site (Morrowind, Oblivion, Skyrim)
Skyrim Database (clothing and armor search engine for Skyrim SE)
ModBooru (clothing and armor search engine for Skyrim LE and SE, Fallout 4 and Fallout NV; no link due to partly adult content)
Mod author's websites
Multiple games
LordGermanicus666 (Skyrim, Oblvion, Morrowind, Fallout 4, Fallout New Vegas, Fallout 3)
zzjay (The Elder Scrolls, Fallout and The Witcher)
Selene310187 (Skyrim, Oblivion, Fallout 4)
Oblivion
Drunken-Crafters-Inn (a group of mod authors dedicated to Oblivion)
Under sun and sky (author: Room207, type of mods: mainly clothes and armor)
Where No One Goes (author: Darigaz17, games: Oblivion, type of mods: mainly clothes and armor)
Lucha's Grove (author: Lucha, type of mods: races, armor, clothes, weapons, companions, resources)
Skyrim
Sunjeong (armors)
immyneedscake (outfits, races)
Halofarm (note regarding the mods)
Ecliptic Orrery (equipment, body skins, UI mods and more)
Team TAL (Take A Look; followers, outfits and characters)
Miscellaneous mod hosting sites
Old Unreal (Unreal 1 and Unreal Tournament 2000)
Deadly Steam (Star Wars: Knights of the Old Republic 1 and 2 plus a small section for the Jedi Knight series)
systemshock.org (System Shock 1 and 2)
Unity HQ (No One Lives Forever and 007 Nightfire Game Series)
Marvel Mods (for games like "Marvel Ultimate Alliance I & II" and "X-Men Legends I & II")