Since DI made the below monster post on the "Best mods" for KotOR in this (
http://www.lucasforums.com/showthread.php?t=203243) thread, I've moved the relevant section of his post here, as I'm sure many of you will find it useful -- j7
I'll try and break this down into small sections, from which you can take your pick, really... I will say that these are chiefly mods I either use or intend to use on my next run-through, barring one or two of the storyline/restoration mods. I'm going to try and pick out as few mods as I can, so this is a very personal and subjective list.
KotOR I
Skins & Textures
Power Overwhelming (
http://knightsoftheoldrepublic.filefront.com/file/Power_Overwhelming;111889) by NiuHaka - absolutely brilliant, and newly released.
Male Head Pack (
http://knightsoftheoldrepublic.filefront.com/file/Male_Head_Pack;84378) by Inyri - less overall wow, but a wide selection and some nice choices, nevertheless.
90SK's K1 Robes (
http://knightsoftheoldrepublic.filefront.com/file/90SKs_K1_Robes;86155) by 90SK - really, really nice robe reskins, but don't miss the patch for this mod.
Models
Weapons of the Old Republic (
http://knightsoftheoldrepublic.filefront.com/file/90SKs_K1_Robes;86155) by T7Nowhere, Mono and svosh - fantastic models, and a lot of them, too.
Scripting/Other
K1 Force Pack (
http://knightsoftheoldrepublic.filefront.com/file/K1_Force_Pack;97281) by Star Admiral - Some nice new Force powers.
All In One Force Power Mod (
http://www.lucasforums.com/showthread.php?t=135226) by Darth333, tk102, Darth Khasei, beancounter, Andargor, & KnightFxr - huge number of Force Powers, and for a long time the Force Power mod for the game. In many ways, it still is.
Storyline/Dungeon/etc
ORD Mandell (
http://www.lucasforums.com/showthread.php?t=136575) by RedHawke - what can I say? It adds a new planet to the game. A bit more on the dungeon-crawl side than I like, but it's still a challenging, fun mod.
Brotherhood of Shadow: Solomon's Revenge (
http://knightsoftheoldrepublic.filefront.com/file/Brotherhood_of_Shadow_Solomons_Revenge;99985) by Silveredge9 - to my knowledge, the biggest story mod for K1 to date. Not a huge fan of it myself, but a lot of people do rate it rather highly, the visuals are good, and it's huge by comparison to most mods for the KotORs.
Korriban Crystal Cave (
http://www.lucasforums.com/showthread.php?t=171014) by Agent Xim - small, but fun addition. Conflicts with ORD Mandell, so be sure to get the patch from AX's site.
Tomb of Jesset Dal'Kest (
http://knightsoftheoldrepublic.filefront.com/file/Tomb_of_Jesset_DalKest;86519) by Darkkender - really, really tough to beat! Worth it if you like a challenge, though.
Other
Animated Launcher for KotOR I (
http://knightsoftheoldrepublic.filefront.com/file/Animated_Launcher_for_KOTOR_I;76942) by Glovemaster - really, really nice launcher.
General Authors-To-Check-Out-All-Their-Stuff List
Prime, T7Nowhere, Silveredge9, RedHawke, Darth333, Mono_Giganto, Svosh, NiuHaka, oldflash, Achilles, Shem, glovemaster, Quanon, tk102, SithSpecter, deathdisco, Darkkender, anyone else I've forgotten at the moment. :p
TSL
Skins & Textures
Force Fashion II (
http://knightsoftheoldrepublic.filefront.com/file/Force_Fashion_II;104261) by jonathan7, Marius Fett and EnderWiggin - since j7 will murder me if this isn't in, I'll put it here. Really, really nice robe reskins on offer.
NiuHaka has released several heads for TSL which are really worth looking at, and 90SK has released a variety of TSL robe mods. Both are slightly more than I want to copy out at this point, but if you click their name in the links to their mods above, you should be able to bring up a list of their other works. :)
Models
Ultimate Saber Mod (
http://knightsoftheoldrepublic.filefront.com/file/Ultimate_Saber_Mod;73530) by ChAiNz.2da, Darth333, T7Nowhere, svosh, and Seprithro - Bit of a must, really - beautiful weapons on offer here.
Final Touch (
http://knightsoftheoldrepublic.filefront.com/file/Final_Touch;72996) by oldflash - some other really nice stuff. Happily these two mods seem to be (more-or-less) compatible. :)
Onderon Museum Upgrade (
http://knightsoftheoldrepublic.filefront.com/file/Onderon_Museum_Upgrade;66535) by Mono_Giganto - replaces some of the items in the Onderon Museum with stuff that's a bit more unique and a lot cooler.
Scripting/Other
High Level Force Powers (
http://knightsoftheoldrepublic.filefront.com/file/High_Level_Force_Powers;43066) by stoffe - really, really great stuff from the stoffe, and don't miss the 2.1 patch (
http://knightsoftheoldrepublic.filefront.com/file/High_Level_Force_Powers;67156), either!
Kreia's Assorted Robe Collection (
http://knightsoftheoldrepublic.filefront.com/file/Kreias_Assorted_Robe_Collection;66487) by ChAiNz et al. - an awesome blend of scripting and skinning, this is a fantastic mod and an absolute must-have.
Storyline/Dungeon/etc
Darksword (
http://knightsoftheoldrepublic.filefront.com/file/TSL_Darksword;66312) by ChAiNz.2da - a small addition, perhaps, but another nice, innovative and fun one, that also brings something to the table - in this case, something like-but-not-a-lightsaber, without altering the game's plot too substantially.
Recruitable Dustil (
http://knightsoftheoldrepublic.filefront.com/file/Recruitable_Dustil;86401) by PrincessArtemis - I have to admit, I've never completed a playthrough with this one, but it's reputation is as the best-written recruit mod out there, and what I have played with it certainly confirms that reputation.
Coruscant (
http://knightsoftheoldrepublic.filefront.com/file/Coruscant_Jedi_Temple;76316) by deathdisco - the first planet mod for TSL. Need I say more?
M4-78 (
http://knightsoftheoldrepublic.filefront.com/file/M478;89207) by DStoney - the closest restoration of the droid planet to what Obsidian intended. Whether that's a good thing or not is really a matter of taste.
Droid Planet Mod (
http://knightsoftheoldrepublic.filefront.com/file/Droid_Planet_Mod;84922) by Darth Shan - a less 'close' and more interpretative restoration.
TSLRCM (
http://knightsoftheoldrepublic.filefront.com/file/TSL_Restored_Content_Mod;111657) DStoney and zbyl2's restoration mod. Not compatible with DStoney's M4-78.
TSL Story Mod (
http://knightsoftheoldrepublic.filefront.com/file/TSL_Story_Mod;85510) by Darth Shan - expands the game a little with some after-end material and some stuff on Nihilus' ship, from what I recall.
Combat Simulation Arena (
http://knightsoftheoldrepublic.filefront.com/file/;75053) by stoffe - really, really fun and often quite challenging arena mod.
Learning the Ways of the Force (
http://www.lucasforums.com/showthread.php?t=168259) by Darth333 - a wonderful mod, which adds a 'Floating Lightsabers' power, just like Kreia uses. You learn it in-game, rather than having it available at the selection screen, which is a nice touch, IMO.
Other
Multi-Stim (
http://knightsoftheoldrepublic.filefront.com/file/TSL_MultiStim;66398) by ChAiNz.2da - four stims in one; saves a huge amount of time buffing before battle, and can be made at the workbench.
Bao-Dur's Charged Armor (
http://knightsoftheoldrepublic.filefront.com/file/BaoDurs_Charged_Armor;66349) by ChAiNz.2da - I was slightly at a loss as to where to put this, but it's a fun, useful and well-integrated mod that makes Bao-Dur a bit less death-prone. What more could you ask?
Realistic Nar Shadaa Skybox (
http://knightsoftheoldrepublic.filefront.com/file/Realistic_Nar_Shaddaa_Skybox;88468) by Sharen Thrawn - makes the skybox a bit brighter and fuller. Altogether an improvement, I think.
Disappearing Rubat Crystal Fix (
http://lucasfiles.com/?s=&action=file&id=1495) by Karstedt - This fixes, you will be surprised to hear, a bug where the Rubat Crystal would disappear... very useful, if not terribly exciting. (Also available here (
http://knightsoftheoldrepublic.filefront.com/file/Disappearing_Rubat_Crystal_Fix;119511) )
Glovemaster's Animated Launcher (
http://knightsoftheoldrepublic.filefront.com/file/Glovemasters_Animated_Launcher;76860) by Glovemaster - another really nice, animated launcher from GM.
General Authors-To-Check-Out-All-Their-Stuff List
Darth333, stoffe, T7Nowhere, Prime, Mono, svosh, Shem, Glovemaster, ChAiNz, 90SK, NiuHaka, jonathan7, SpaceAlex, deathdisco, RedHawke, and many others, I'm sure, who for the moment escape me.
As to where, aside from KotORFiles, I'd check the "Where can I find mods?" thread in Holowan. :)