Backup to DVD/CD - options?

I regularly backup my files to DVD/CD. One problem I haven't been able to solve is the hassle of setting up this backup. For instance, if I have 8 GB to backup, then I have to figure out how to distribute those 8 GB amongst two DVDs. With my DVD burning software, I just keep adding directories to be burned until I hit the limit of the DVD. You just have to keep track of what files should go on DVD 1 and which should go on DVD 2.

There must be an easier way. Perhaps some software that you can specify the directories to backup and it creates 2 directories '/DVD1/' and '/DVD2'. Then you just need to burn all the contents of /DVD1 to the first DVD and /DVD2 to the second DVD. Is there software to do this? Or perhaps some backup software that will burn to DVD and know what to put on the 1st DVD, etc.

Any advice on this would be great. Oh, and free would be great also.

Thanks,

Aaron