>>Another option you can consider (even cheaper per GB, but not as re-usable) is a CD writer. Some can be written only once, some more than once.
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>The only problem with CD burners is that you're limited to 650Mb. If that fits the bill, fine, but it doesn't take much these days to exceed that. You can get 20Gb Travan tape drives for under US$300 now, and that is the option I would probably go with. It's relatively cheap, and the tapes are reusable (though saw a Circuit City ad today for 100 CDRs for US$9.99 after rebate, so who cares about reusable?)

Some modern backup packages can span CD-Rs, removing the space limitation (however, you still need to be around to change them when prompted).

A CD-based backup is also a very fast way to get back to normal operations following a major disaster like machine theft, fire, etc.