Burn to the Brim is a “Utility for grouping files and folders together in the most efficient way to fill up an entire CD (or other medium)”. It runs on the Windows platform and could be useful if you’ve got gigs to back up:
The program analyses the files and folders in a folder you specify, and groups them in the best possible way. Most likely BTTB will find a near-perfect solution for you within one second, and a perfect one in just a couple more.