As I've said before, I'm not terribly original in this matter, instead mostly "converting" other folks stuff to TFT for my players. The one I've been working on most recently is
Dolmenwood -- which has just the right "feel" for me in terms of setting, and is a nice, small sandbox with a lot going on and a lot of NPCs to interact with.
Posting it here, of course, would be highly illegal (I would think), but you can order a copy (and get parts of it for free) over on OneBookShelf's various rpg pages (go
here to look at it). It's nicely thought out and even ties into things like Ed Gillespie's
Barrowmaze (they have a place where you could put that, if you wanted to) for those needing a megadungeon to liven up play...
Others that I've done something similar with were
Wilderlands of High Fantasy,
Forgotten Realms (mostly for the complex setting, not necessarily for the details in the adventures -- the Red Wizards make a wonderful villain group, though), and, to a much lesser extent, the area around
Rappan Athuk. (Can you tell that I like sandboxes and megadungeons? ;-) )
Oh, and of course,
Keep on the Borderlands!
(
Edited to add link for Dolmenwood material...)