These things:
http://www.buffalotech.com/products/...e/terastation/

ROCK!

I have two in my office, one backing up the main data on all workstatons, and the other backing up the backup. Had one of the RAID disks go bad, it told me so, I replaced it, and it rebuilt the array in about 12 hours (that's with about 1.3 TB of data).

I also have an external USB HDD that I backup the REALLY critical stuff to (email PSTs, My Docs, digital photos, MP3s) that always leaves with me when I go out of town. In fact, it stays in my pickup except for when I am updating the backups.

Offsite (like, on the Internet) would be an option but not for massive amounts of stuff. For example, I don't want to back up my 100 gigs of MP3s via the web. But also not for sensitive items - depending on the laws of the country where the backup server is hosted, you might be opening yourself up to any number of identity theft issues and etc.