Just to follow up on a few things - DeVeDe isn't for making backups of pre-existing DVDs (though there are ways you could use it for that), but for authoring DVDs from video files in various formats. If, for example, you have a tv show in xvid format from ... somewhere ... you can easily use DeVeDe to convert it to mpeg2, create the DVD tree structure, then wrap it up as an ISO ready to burn to disk. I've heard that some people do this.

My brother uses k9copy to back up the DVDs for his son (my nephew!), since the originals in the hands of a 3 year old tend to get scratched, broken, or hidden under the dog's bed. K9copy, as far as I've seen, produces good quality back-ups.
Remember, though, that all such software breaks copy protection (
CSS) and is therefore illegal in many countries, including the US (
DMCA) and possibly Canada in the future.
Tom