BitDefender, F-Secure, Avira, and Kapersky all offer
free rescue .iso downloads that will allow you to burn a rescue CD to boot from. The Kapersky .iso does not work on PC since it uses a Linux kernel that is incompatiable with my motherboard.
The Avast rescue CD is not free but you do receive a physical CD. Problem is it has bugs that to date are not fixed. Most notably the inability to select drives to be scanned. It does make an attractive coaster however.