I would like to create an image of the Ubuntu 9.04 system running on my desktop PC, so that in the event I mess something up I can return to a system, that is already setup and 'tweaked', as apposed to dropping the install disk back in and starting again.. I would also like to look into doing this for other ubuntu pcs over the network and hosting these recovery images on my desktop pc...
On debian, we use etckeeper for the system configuration files (essentially etc under revision control with some helpers) and I expect it's available for Ubuntu too.
For user files, each site seems to have slightly different desires. I think tarring it and rsync'ing the tarball is one of the most common methods we use. The --rsyncable gzip option is useful then, set through the GZIP environment variable.
I'd be interested to know if people are loving any of the larger backup tools on small single-server sites yet...
Hope that helps,