Originally posted by Big Mac:
Your user's trash is: ~/.Trash
There is also a .Trashes on the root level of your startup drive, but I don't know what function it serves since ls is denied there.
.Trashes exists at the root of every volume, I don't think you should have one on / necessarily though. Anyway, it exists so that you can move stuff to the trash on other volumes than your root partition without moving stuff to ~/.Trash (which would obviously copy it to your root partition).
There are subfolders for each user in .Trashes, like .Trashes/501 etc.