I recently upgraded my network at home to 1GB. I wanted to find a software that would backup my files incrementally. Meaning, as a file was changed, its backup would also be changed. I was able to find FolderShare. This is now a free service from Microsoft Live.
You simply download the software onto the 2 computers you want to synchronize. Point to the folder(s) you want to be in sync. and the software does the rest. As you change files on one computer, it is backed up on the other.