This document is an interesting extract from Real World Linux Security by Bob Toxen that details how to regain control of your system after it has been cracked.
OpenBSD - The proactively secure operating system.
Nice article. I skimmed through it and saw a lot of useful tips. So far, I haven't had to worry about regaining control over any of the systems I administer, but it's always a possiblity I need to be on the look out for. Thanks for the help.