For a school project a while ago (computer security) I had to answer the following question: "How easy is it to crack a protected wireless network?".

Here you can download the resulting paper:
users.pandora.be/___/school/kraken_WEP.pdf
It's in Dutch. (to show we actually did it ) Hopefully it will be useful for others.

It is a rather detailed description (being a newbie to Linux) of how I used backtrack to crack WEP and described which problems we encountered doing that. e.g. wireless card got stuck in monitor mode.

I used a backtrack 2 beta livecd, a laptop with a built-in PrismGT wireless card and the following three guides:
aircrack-ng.org/doku.php?id=newbie_guide
docs.lucidinteractive.ca/index.php/Cracking_WEP_and_WPA_Wireless_Networks
forums.remote-exploit.org/showthread.php?t=1556

Enjoy
Gfy

P.S. Because I can't post a new topic in 'Tutorials & Guides', I'm placing it here.