Campaign settings for AD&D include Forgotten Realms, Planescape, Greyhawk, Dragonlance, Dark Sun, Ravenloft and Spelljammer. Only FR, DL and GH survive intact into Third Edition, but there's nothing to stop you using the old material or making up your own. Imagination is the key to good AD&D. I was once a hack and slash player, but that lost its appeal - making the players really think is so much more fun. Planescape and Forgotten Realms are best for this, IMHO.