My usual advice to DMs that ask for traps is to tell them, "No. You don't actually want traps."
Traps are some of the most misused aspects of DMing. They've been used to promote pure adversarial DMing, and they tend to create improper DM fantasies in that it's almost impossible for most DMs to place a trap and not hope it goes off. The more awesome the trap, the more this is true which leads to all sorts of escalating bad DMing decisions.
You know a trap thread is going bad when someone mentions Grimtooth in an approving way. It's like a how to guide of how not to use traps.
I'll go ahead and push my reputation for arrogance further, by saying I'd go so far as to say I've not seen a single artistic use of traps described in this thread. It's all been pretty wretched advice.
The only one I like a little is breaking pipe trap depositing the players in a combat encounter, but that's more of "Trap as Scene Framing" sort of thing than it is using a trap as a scene or encounter itself. The poster that called it 'dramatic entrance' had the right of it. It's not a trap per se, just a way of heightening the tension of a combat. Ditto the "spray blood and release the beasts" sort of trap. There is nothing wrong with that sort of thing, and in fact, framing a scene tensely like that is a good thing.
But that's not really a scene built around navigating a trap itself.
Some questions should always be asked of any trap:
a) What maintains the trap in its finely balanced state? The more elaborate and fragile the trap, the more one wonders why it's not already broken.
b) Why did someone bother to build the trap, and in particular why did they bother to build it right where they did? Quite often you see these lethal death traps on hair triggers in the middle of the residential quarters of someone's lair. You might as well have a covered spiked pit trap in the middle of a busy city street.
c) Why is this trap fun for the players? Is the interest in the trap mainly an interest in showing off? Does the trap make the game more or less tedious?
d) How is the trap interactive? Do the players get to act on the trap, or does it just act on them?
e) How is the trap avoided? What signals should an observant player receive that the environment contains a trap? If you are trying to cover up these signals rather than create them, it's a good sign that you as a DM don't have the right motivation. It's trivially easy to create inescapable death traps, or at the least traps that act mainly as unavoidable hit points taxes. What's hard is creating a trap that is fun for everyone. Make sure that's your goal, and not playing gotcha with the players. Because if it is the later goal, what you are saying is that all the time and in all ways, you want players to spend 10 minutes tediously checking against traps before they do anything.
Some further reading:
http://www.enworld.org/forum/showthread.php?348572-What-s-your-favorite-trap
http://www.enworld.org/forum/showthread.php?311219-Honoring-Pit-Traps
http://www.enworld.org/forum/showth...e-on-traps-Tomb-of-Horrors-NOT-for-my-players
Update more reading:
http://www.enworld.org/forum/showthread.php?403969-The-Awesome-Endurance-of-D-amp-D-s-First-Modules
http://www.enworld.org/forum/showthread.php?251072-Two-Dozen-Nasty-DM-Tricks