Ok, so it won't work with Mac (yet?) but I've been very happy with my 120GB Mirra box. It just deals with backing up files without any intervention at all, from your entire (PC Windows) home network. It even keeps previous versions of files, which can be a lifesaver, and allows you to selectively invite external users to access sections of your backups (eg family can browse your photo collection, even through a firewall).

Very slick, though it'd be even more slick if they offered an online locker service that the mirra box would also deal with keeping up to date....

http://www.mirra.com