The easy way: Buy a duplicate hard drive, and use cron[1] and rsync[2] to schedule an automatic nightly backup. If you have stuff that cannot be backed up directly by file copying (such as live SQL databases), use their dump procedures, which are specifically for safe copying. When your hard drive dies, just switch to the other, and buy a replacement backup drive. It doesn't need to be local, either - rsync is quite bandwidth-efficient. Also: Test the backup now and then!
[1]: http://en.wikipedia.org/wiki/Cron
[2]: http://www.samba.org/rsync/
If your data is worth asking strangers on the internet for recovery advice, it's worth spending an hour to set up a backup system.This has saved me from drive crashes twice, so far.