Fravia's pages of reverse engineering
Fravia's site is the site to be if you're looking for tutorials on reverse engineering.
MakeCrack
Check out the project list of the Coding Lab for more info about this. MakeCrack is one of our projects and should make it easy for you to make patches and other cracks.
CrackStore
The name says enough...
Sudden Discharge
If you're interested in encryption, this is the site to be. You'll find many info on all sorts of encryptions you can think of here.