Dropbox – 2GB free online storage that can be accessed and synced from any of your computers. Use the link here and we’ll both get an extra 500MB of storage. Will also sync to your Mobile.
I use SourceKit a plugin for Chrome to write notes and some code to my Dropbox account. Any files written in this way become accessible across any PC’s I have synced to Dropbox.
There are a couple of backup tools that will allow you to backup your WordPress site to your Dropbox account. I personally use BackWPup. I also send a backup to my Gmail account for longer term safe-keeping.