Any external drive with a decent consumer rating at Tiger direct will do.
http://www.tigerdirect.com/applicati...rd-Disk-Drives
Then get Syncback, it's free:
"It lets you define multiple scheduled backup jobs so you can just set 'em and forget 'em, allowing users to create specific backup jobs for certain folders or file types. You can control the way files are compared and selected for backup: the program comes with ready-made profiles to make the process as easy as possible. It's hard not to like that SyncBack doesn't use many system resources when working in the background, and backups can be set to export their logs to an HTML file for easy viewing. All in all, it's an excellent choice for home users and small businesses."
http://www.download.com/SyncBack/300...-10413802.html