Don't panic...I used a Puppy Linux Live CD to repair my Ubuntu 10.10 install
after a goofed up update, I think the power went out. All I did was boot it up
and it offered to fix it, but you can also mount the hard drive and copy stuff
to USB first if you want to, just remember to unmount before you re-boot.

http://www.puppylinux.com/download/

You can also find it via Distrowatch.