I'm with danzig - for nostalgic purposes I'd like to see some of the original modules made into quests.
Example - my very first module ever - Keep on the Borderlands
This could be made into a wilderness area like 3BC or Tangleroot. You have a Keep, and then the a wilderness area that leads to the Caves of Chaos, where there are entrances to Kobold Lairs, Bugbears, Ogres, Goblin/Hobgoblin, etc.
I think my other favorite would be the Against the Giant series:
Steading of the Hill Giant Chief
Glacial Rift of the Frost Giant Jarl
Hall of the Fire Giant King
I think this was the opening to the Drow series, can't recall the name.
Another good one would be the 4 Slave Lords quest chain.