Is there a live cd out there that I can just pop in and get instant network access to whatever's on the machine's drives?

This would be very useful in lots of situations, one specific being when I am at work and someone's computer comes in unable to boot, I could just pop in the CD and examine the drive from another computer and make a quick backup.

Knoppix, at least, comes with samba installed by default, and I think it only needs a bit of setting up to get it to share its drives. Perhaps you could set it up on one system and save the profile to a usb stick that you can use to boot with on other machines. It might not be perfect, considering how varied people's computers can be, but if you set up a rather generic configuration you might be able to use it with most setups.

Another option would be to build your own customized live cd. I know there are webpages and scripts out there to help you set one up.