Crashplan is a really useful solution to a problem most of us have: it's tedious and/or expensive to backup offsite.

The only cost is a $20 license for the computer you want to back up. (Being the recipient/storage site for backups is free.)

Offsite backup is a critical part of protecting your data. Crashplan makes it easy and cheap. I have used this software to backup from a Mac to a PC. I have used it to allow three different locations to backup to each other. I have restored from backup. It's easy (so easy that I have used it to migrate data from an old computer to a new one).

If you do include a Windows computer in your backup strategy, remember to ensure that your Windows firewall & your security suite firewall (e.g. Norton) will let Crashplan through.

I have a router with a firewall, so I had to open a port on it.

The whole thing is dead easy, though. Two of my locations use Dynamic IP addresses and are behind routers (so they are NATed and use 192.168.x.x addresses). Crashplan just takes care of it.
Crashplan email support is friendly, helpful, and prompt.

This is the offsite backup program that I've needed - I highly recommend it!