"The word 'radical' derives from the Latin word for root. Therefore, if you want to get to the root of anything you must be radical. It is no accident that the word has now been totally demonized..." -- Gore Vidal
If you are looking into how to start learning reverse engineering and exploitation you better hold on to your butts.
Matasano recently release a set of hacking challenges called Microcorruption. The site provides a list of targets. Each target is a "lock" that you are contracted to reverse engineer and exploit. The web interface provides an entire debugger and disassembler for you to use.
It's very well made and very fun. The challenges start easy and get harder. It also starts with a full on tutorial to get your feet wet even if you've never done anything like this before.
I've started up an official discussion thread in the forums for discussion. Please no spoilers but don't hesitate to ask questions if you get stuck on a challenge.
Get to it! Drop in and list your success in the discussion thread!