Several links to VOB tools at
http://doom9.org/index.html?/software.htm. I definitely recommend downloading DVD Shrink if you don’t already have it – great ripping tool. I’ve heard a couple of people recommend VirtualDubMod and VirtualDub Mpeg2 for the VOB to AVI.
You can also go to Videohelp.com and do a search for "VOB to AVI"; they've got several programs listed.
Hope this helps.