Kotor 1:
Redhawke made some planet and new area mods: Ord Mandell (
http://pcgamemods.com/7699) and Weebul and Utiinii's (
http://pcgamemods.com/8012).
I made new areas too but it was a joke mod:
http://pcgamemods.com/u/3451/) (if you don't know the people at Holowan it will probably be quite weird).
Not a new area but definitely worth it, Tanesh's Mekel recruitment mod is the best recruit mod made until now:
http://www.starwarsknights.com/kotor1mods.php) (all the mods on this page are good)
Xavier2 also made mods based on the movies if you like it:
Some other goodies for your override folder which add to the storyline (some material got cut form k1 too):
- Bastila on Korriban :
http://pcgamemods.com/5374/)
- Deadeye Duncan on Manaan:
http://pcgamemods.com/5410/)
- DS female alternate ending:
http://pcgamemods.com/5326/)
hehe and a small goodie I always use when I play DS:
http://pcgamemods.com/8708/) (got to plug my stuff somewhere :p)
If you look at the mods at pcgm you'll find much more.
As for Kotor 2, there is GSccc's Rise of the Sith Demo (
http://pcgamemods.com/15029/) (I didn't tried it due to file size and time issues) and the USM mod:
http://www.lucasforums.com/showthread.php?t=149509) (It's new item but it also fixes a number of issues in the game and all sabers have been integrated in the storyline)
Moving this to the Modding requests forum ;)