I really like my Maxtor “One Touch” backup drive. I got the 300 MB version (has both Firewire and USB 1.1/2.0 interfaces). I use the Firewire interface and connect it to my server. It was about $330 at CompUSA.
Note that the “one touch” button just launches any program you’d like, including backup software. Since I schedule a nightly incremental backup of data, it really isn’t necessary for me. If you had one of these one-touch drives attached to each of your computers, then I can see value in configuring it to do an incremental capture of the local system and data on demand.
There’s a flash demo available as well.
I use this for data file backups from shared (and secure) data folders across the home network. The Dantz Retrospect Express Software is very good. It takes a little getting used to, but then it works reliably.
For image backups, I recommend a copy of Norton Ghost 2003 for each machine to be backed up. Configure it so the image gets dropped to a file share on your server (the Maxtor drive, in fact), and everything is centralized for backups.