i LOVE having a NAS on my home network. (oh, Network Attached Storage). easy to share files, backup stuff, use as a music server, etc.
the nice thing about the NAS's is that the interface is painless, just plug it into your router, type in the IP of the NAS, and configure. (the diff between just an external hard drive and a NAS is the software on the NAS box and the connectors available)
When I go home, the laptop automatically joins the server, and my backups automatically start and backup to the NAS.
Buy.com - SimpleTech 500GB SimpleShare NAS Office Server Storage - STI-NAS/500