every book’s a sourcebook: Traps from The Ginger Star
The Ginger Star by Leigh Brackett
Another good classic D&D trap from The Ginger Star
: A windlass at the top of a staircase that drops part of the staircase. You can either go old-school D&D, and have a goblin run out and turn the windlass while the PCs are on the stairs (falling damage, no save, go down a dungeon level, roll on the wandering monster table) or 4th edition it and have the PCs have, say, three turns to fight their way up the stairs to stop the goblin before he can turn the windlass 3 times.
I think I prefer the old-school method. It feels so classic I’m surprised it’s not in the AD&D random dungeon features appendix.