Who remembers those sites where they gives you hacking challenges. Anyways, I thought now that I've learned a bit more about debugging and disassembling I'd give it a go; however, I can't remember where in the world I found it. I recall a post on these boards about them and I'm wondering if anybody has a link stuck in their favorites.
www.hackerslab.org for unix hacking.
www.try2hack.nl for windows style "hacking" (Easy... :/)
Those are the two I have done. HackersLab is quite fun :)
Good Luck Eth.
hack.datafort.net
get past level1 and get a cookie :|