Because nobody really did it - I'm creating this topic for mods, unofficial patches and any other stuff you would find for Knights of the Old Republic game series... but mostly for two mods that are out there, namely: KotOR 1 Restoration and, foremost, TSL Restored Content Mod.
Most of you know the latter - KotOR 2 was, sadly, rushed and many content was just cut out from the released game. Thankfuly modders gave there all to restort what Obsidian tried to put in game, fixing many bugs along the way. Of course the game can be played without it, and finished, but this case is simillar to Vampire the Masquarade: Bloodlines - the amount added by modders is just insane. Quests, items, fixes (this are important, too) - they make the game so much more complete experience for a player. So, with no futher addo:
KotOR 1 Restoration:
As it was said on Deadly Stream site - there is not much to this restoration mod, because BioWare did quite a good job and implemented most of things they planned (compared to KotOR 2, at least). Not that obligatory, but still recommended. All instruction are on DS site I linked, so I think there is no need to explain it here.
KotOR 2 TSL - Restord Content Mod:
The main reason I'm creating this topic - most people usually knows about it, but maybe... just maybe there will be some new players who were never interested in it before so - this mod is mandatory. Looong page of changes, lots of content restored (bada tss), fixes - there's too much to count. If you want to fully experience KotOR 2, you'll be needing this. Again - you can find instructions on their site.
M4-78 Enhancement Project:
This one is a add-on for TSLRCM - it adds a new planet, M4-78, with voiced dialogs, quests and items. It requires TSLRCM to be played and althought modders say it "Your actions on M4-78 bave impact on other planets (...)" I haven't check it myself, so can't really say how much 'must' this mod is. Maybe someone in the comments will add their opinions (hopefully someone will add something here...), so you could decide on your own if this is worth installing or not.
OK... I think it's everything, for now at least. Don't forget to leave your kudos for the good folk who created the mods and Deadly Stream for hosting it. :)
And thank you for reading this far. :D