I backup my entire computer on a weekly basis, more if I've been inputting a lot of information, onto my SimpleTech Signature Mini FS-U25/320H 320 GB USB 2.0 Portable Hard Drive (in Black Cherry).
I also email myself a copy of my main genealogy file, both as a Legacy file and as a gedcom. I am hopeful Google documents will one day include gedcom's as a supported file, but not yet...
My worst fear would be to spend a whole day adding new information and then just having the files disappear or get corrupted.
Next on my to do list is to start backing up my blog as well.
Don't lose your all your hard work - join us for Data Backup Day!