Hacking Games:

Hack me http://loginmatrix.com/hackme/.
Try2Hack http://www.try2hack.nl/.
Hack this site http://www.hackthissite.org/
http://www.slyfx.com

A teeny bit more advanced:

http://www.roothack.org/
http://www.hackerslab.org/eorg/
http://ddll.sdf1.net/archives/000718.html

For Coders:
http://lightning.prohosting.com/~thegame/

Original Thread

Special Thanks To:
shadowdancer123, Cop, gman24