Here's a few sites that should give you some cool mods,
www.jk3files.com)
www.lucasfiles.com)
www.pcgamemods.com) (PC Game Mods is down right now)
www.jedimoves.com)
Those are the main sites for JK2 and JK3/JKA. Just so you know the SP SDK hasn't been realeased so don't expect to see any code changing mods for SP (you wouldn't believe what can be done to SP even without the SDK). Even so a good 60-70 % of SP is still editable.
Heres a few of the things that can be changed in SP:The speed of attacks and weapons, the range of weapons, ammo and item related things can be edited and added (if you wanted you could give yourself 10,000 ammo or something like that), NPCs can be edited;added;deleted etc., you can make new hilts and sabers, you can make new vehicles, you can edit and change every sound;effect;visual effect;graphic effect there is and you can edit the way saber blades look and even the graphics if you know how to mess with shaders, you can edit the music of all the levels, you can edit the storyline and add and create new levels and cutscenes and script events and happenings, you can edit;add and change the models and skins in the SP Player selection screen, you can make new animations to replace old ones and edit almost anything animation related, you can edit saber attributes, you can edit textures and models and add new ones, you can edit every single aspect of the menu system, and more.
Thats not everything but most of the things you can do to SP. You can also edit things like saber damage, the knockback force of certain force powers and weapons, give yourself the ability to do taunts, give yourself unlimited force, and do loads of other crap via console commands and config editing. Like for example, I binded a key via config editing to do the normal taunts for each saber and I replaced the dual taunting animation with aloras dual saber throw animation and now I can throw both of my sabers at the same time if I have duals. I even replaced the staff taunt with the dual saber throw animation so I can throw my double-bladed saber.