You can use a couple of good freeware DVD Authoring tools: DVDFlick (Windows) and DVD Styler (Windows/Linux).

Note that DVD Styler doesn't re-encode VOB and MPEG files if they use the following settings:
-Video 720x576 (PAL) or 720x480 (NTSC)
-Audio MP2 or AC3, 48000Hz
(despite the fact that DVD compliant videos allows more flexibility)