Here's an easily modifiable script that uses hard links and rsync. I used this as our office's starting point and now have a system that:

• creates a local snapshot every night and stores it on a separate drive;
• archives a copy from the night before for only the storage cost of the changes;
• writes off to an external drive every weekend.

The nightly back-ups mainly account for users accidentally deleting files or saving changes they wish they hadn't rather than hardware failure. Since it's all just stored as a copy, I can mount it over the network if necessary or archive the the snapshot to external media anytime I want. It doesn't require any downtime to back-up or restore on our setup, but if you were dealing with some more complex services you might need to make som allowances.

and organizations to these entities are not tax deductible.

Of course...that should have said "and donations to these entities are not tax deductible."

/me goes to emerge coffee