Alright, so what's the best way to go about making a good mob trap in Minecraft? Here are some traits I'd like to have in the trap:
Easy to build.
Although I have (or can easily obtain) whatever materials needed for a mob trap, I'd prefer it to be simple, as I have a talent for melting myself in lava, falling down extremely deep pits, and other unfortunate accidents.
Preferably, once I build this trap, I'd like it to be mob-proof, with no chance of 3 spiders clogging the trap for an hour. Additionally (although this isn't quite so important), it would be nice for there to be an escape route, in case I accidentally fall into the trap myself.
Self-explanatory. I want the trap to gather all of the items (losing string I don't care about, but I want to collect all the useful drops like gunpowder and arrows), and deposit them via water/whatever method works at a nice drop-off point outside the trap.
So, given these three preferred qualities, what would be some good traps for me to build?