Jack99
Adventurer
ThisAlso: Castle Whiterock (Goodman Games) is probably the best designed mega-dungeon I've ever seen in terms of fleshed out content. Amazing.
And this..Rappan Athuk Reloaded is also a great one.
Aside from that, I have always gotten a lot of mileage out of the 2e Undermountain boxed sets.
But really, Castle Whiterock is, if you can find it for sale, really in a league of its own, IMO.