The Dark Forces TC mod started off as a mod for Jedi Outcast. That was back before people even knew that Raven was developing Jedi Academy. When news of the sequel emerged, the team decided to change plans and make the mod for JA instead of JO. The reason; JA's extra features (aka more weapons, textures, large creatures as enemies) makes it much easier to create that old school Dark Forces feel than JO allowed. However, they did create a one-level demo of the mod for JO before making the switch. That level can be found here.
The team is still hard at the mod, and is almost done with a three-level demo for JA.
As for some of my favorite mods, there's a ton of great ones out there. For SP levels and mods, the first Dark Forces demo and the Colosseum mod are two of the best. A few other great ones that come to mind are Dash Rendar: Resurgence, Ladders 1 and 2, Spice Mines of Kessel, Project Lighthouse, Kyle's Nightmare, Nar Shaada Once Again, Hoth: Imperial Base and Escape from Takron-Galtos (dang, I remembered more than I thought!). All of these can be found at www.map-review.com