This may sound stupid, but as cool as some of the return to adventurers are, I wonder if just updating the originals to the new system, and making appropriate CR changes as needed, wouldn't be the way to go.
I'd like return to the Isle of the Ape and return of Vecna Lives!
TSR released some good modules, but most you can buy and convert if you really want to. What seems like a good idea to me is release a couple of books of converted dungeon adventures from years gone by - the top 20 as voted on by the public. Redone for 3.0/3.5 of course.
