I've just processed AC-DC Live at Donnington for my N810 and I'm knocked out with the quality of picture and sound. Here's how I did it in what I've found the least complicated way.

Download DVD decrypter and point it at your DVD. It does the rest with very little need for intervention. If your DVD's not encrypted, obviously you won't need this stage.

Download autoGK and follow the simple instructions to process your DVD to a one piece .avi file. Make sure to include all the sound files in your desired language.

Feed the ensuing .avi file to Nokia IT Video Coverter and copy it to the IT. That's it.

The reason I like this is that you have 3 programs (all free, though personally I do contribute) which each do one thing and do it well.

I tried feeding the VOB files direct to the IT Video Converter but it wouldn't accept them.

This way may not be the quickest but it seems to be fairly bullet proof. The programs I mention I use in Windows but they are available for other platforms.

I'm aware that you shouldn't copy DVDs but since I don't watch them on a TV, I will buy them to watch on the IT. If the makers won't supply me with the necessary files, I'll make them myself.

i use DVD Catalyst 3
convert movies straight from dvd then to my NIT
best and fastest i used so far

Ideally, you wouldn't encode the video twice. It'll be slower and the end result will have lower quality.

Mencoder has worked well for me as a quick-and-dirty*, one-step DVD to N800 encoder, but it can be intimidating to someone wanting a simple GUI app.

* I say quick-and-dirty, because if I was worried about the best quality result, I'd spend a lot of time crafting a perfect AviSynth script to process the video.

I use dvdrip (linux only). It provides a fairly powerful frontend to the transcode application.

Have you seen this plugin that someone wrote for ITVC? http://code.google.com/p/tutorial2tablet/