The Magenta Key will bypass all traps, and the Pink Rosary confers permanent immunity from traps. The Bright Green Scroll (whether small or large) will remove all traps in the current level.
Other items yet to be identified may bypass or deactivate certain traps as well. In particular, certain Rings and Cloaks appear to confer immunity to particular traps.
The game's collision detection will occasionally register your hero as touching a trap even if you're clearly in the next square over. This can happen even if you're separated from the trap by a wall.
Once in a while, the game will "ding" you for a trap right as you enter a room, even if you're nowhere near the trap.