If you want retain the movie in video DVD format (i.e. as IFO-BUP-VOB files), DVD Shrink is one of the best (and free) alternatives.
Also CloneDVD is an excellent choice, but too bad is not free
Another free alternative is DVD Rebuilder, but it requires a powerful CPU to make a backup.
If you want convert the movie in a different format, like Xvid for example, then one of the best (again free, and also very easy to use) software is AutoGK.
If you want use a different format, then post here for more details