If you are going to go this route, buy a CD Re-writer.
If you get something like the Phillips 400 series, it comes with bundled Easy CD, which has an option to configure a re-writeable cd as a hard drive. So for example, you can drag and drop files straight onto the CD and it will write them automatically. If you update a file, and drag it to the CD, it will ask you if it should update the backup and so on.
Excellent for all backups, and leaves no excuse for not doing it!