It depends on how elaborate you want to be in your editing. If you just want to make cuts, you can use a simple program like VideoReDo TV Suite.
Womble Mpeg Video Wizard DVD (ridiculous name), is a very good editing program for the mpeg2 codec found in dvd-video. There is a free trial that is fully functional if you'd like to try it.
The main advantage of those two program is that they do minimal re-encoding around transitions and cuts.
If you want a more general purpose editing program, look at Adobe Premiere Elements.