Here’s my backup solution. Note that I have a computer for personal use, and there’s no sensitive files. If you adapt it, may be useful. As my USB port is broken and I haven’t gotten around to fixing it, I use rewritable DVD’s. You can substitute CD-RWs or USB drives.
Documents — Google Documents, although sometimes I use a DVD-RW.
Pictures — DVD-RW. I also have a bunch on ImageShack, but as I have several thousand (don’t even ask) it takes a while to upload.
Music and Videos — DVD-RW, as usual. Sometimes if I’m sharing them, I keep them on MediaFire.
Installers — I always keep backups of freeware installers — the websites often go down. I put them onto a DVD-RW. (You’re probably wondering why I’m not running out of them by now. I have about 10, and each of them holds almost 5 gigabytes. Currently, only 3 or 4 are in use, and none of them are completely full.)
Bookmarks & Firefox Addons — Here’s the neat part. I use Firefox, so I use Foxmarks to backup my bookmarks. Within my bookmarks, I have a folder called “Addons,” where I keep all the addons I use (or interested in). So if I have to format my HDD, at least I can reinstall the addons!
Other — Either DVD-RW or MediaFire. Depends on if I’m gonna share it or not.