elannert
As Ivan mentions, there are a lot of services for online back up available. I tried "Backup service" in Google.
If you're just looking for an extra precaution, rather than using this as your main backup solution, you could simply rent space on an FTP server and set up your own encryption and compression and saving routine. No need for an expensive host with a dozen different precautions.
If you use a good online backup services you should be able to dispense with the tape back up altogether (but make sure it's a reputable company, not one that could disappear any day).
One idea I've seen bandied about the non-profit world is for similar organization's to provide back up storage for each other, so you would partner with a similar non-profit (preferably one that wasn't too close geographically) and each host the other's back up data, probably via a VPN of some sort.
If both organizations already have the WAN tools in place (high bandwidth connection; some form of secure, remote connection) this could be an inexpensive way to build a fairly robust back up service.
Helen