I hear it all the time "my hard drive's died now my works lost". Or "my laptop was stolen and all my saved files have gone".
All you need to do is install dropbox and whenever your connected to the internet it will automatically back it up!
If you have more than a few gig of files to back up (which if it's just a few spreadsheets and word docs it won't be). Then use an external hard drive. A really good program I found is called Allway Sync.