AVG Rescue CD
Base: Linux (77 MB)
Configured to create either a bootable CD or USB drive
Signature Update: Online update or downloaded signature file

Avira AntiVir Rescue System
Base: Linux (47 MB)
Signature Update: Downloaded signature file

BitDefender Rescue CD
Base: Linux (228 MB)
Signature Update: Online update or downloaded signature file

Dr.Web LiveCD
Base: Linux (65 MB)
Signature Update: Online update

F-Secure Rescue CD
Base: Linux (155 MB)
Signature Update: Online update or downloaded signature file.

Kaspersky Rescue CD
Base: Linux (103 MB)
Signature Update: Online update

Norton Recovery Tool
Base: Windows Vista PE (241 MB)
Signature Update: Online update

Read more about it at: http://blogs.techrepublic.com.com/security/?p=3803