The one internet link I will always regret losing was a tool to mount PartImage's bzip-compressed/sparse images as a virtual drive...

I've tried to find it again several times to no avail. I have a bunch of backups that I would be interested in accessing without having to restore to disk in their entirety (as explained below):

http://unix.stackexchange.com/a/52684

Edit: Apparently a sparse VM disk works:

http://serverfault.com/a/47075