Ideally going straight from VOB to flv would be best for maintaining quality. However, VOB files are quite compressed and not designed to be decompressed or converted - it's a bit like editing a PDF. It is always best to get the original source video.

A program called "handbrake" is capable of converting VOB to mpeg - I can't remember what the Flash Video converter can handle, but it can prpbably handle mpeg. Since that is what I have at home, I can not recommend any free flv converters, however I think this web site is quite popular:
http://www.rivavx.com/

EDIT: I see it is service videos, so probably recorded onto DVD?

Thanks for responding and yes its church service videos. My church gives me dvds and I rip them using Dvdshrink to Video_TS folder. What are some recommend file sizes for the end product because I don't want the file size to be too big?

A program called "handbrake" is capable of converting VOB to mpeg - I can't remember what the Flash Video converter can handle, but it can prpbably handle mpeg. Since that is what I have at home, I can not recommend any free flv converters, however I think this web site is quite popular:
http://www.rivavx.com/

EDIT: I see it is service videos, so probably recorded onto DVD?

The target file size you should aim for depends on:
1) where you host it. If free, then there are probably some documented limits imposed. Start with those.
2) (if not free): your budget. Estimate how many people will download them, work out how much one movie can "cost" to download, and then work out it's maximum file size (keep in mind, people may want to watch all 3 parts).
3) your target audience's accessibility to broadband. Obviously, if you live in dial-up town, you have to try to cater to that (I hope you don't!)

Factors that contribute to the filesize are:
1) picture resolution
2) frame rate. You can often get away with 15 fps. The sound is the MOST important.
2) sound/picture quality <-> compression level
3) stereo/mono sound
4) codec and compression method (including CBR/VBR, one-pass/multi-pass)
5) the amount of motion and changing picture in the movie. If you have large areas of unchanging/plain-colour backgrounds then you will fare much better when it comes to compression. It would be worth designing the backdrop to your stage with this in mind if possible.

For broadband users, a good size resolution (600x400) can be delivered nicely at a bitrate of 5-600 kbps (bits) if using something like H.264 as the codec. However I am not so familiar with FLV's options (it has been a while!). I am more familiar with using Quicktime Pro (which is a nice alternative to flv these days with the popularity of iTunes/iPods etc).

Now I feel dorky in posting the same thing to 2 old threads in one day but, I'm comfortable with dorky.

I have been using Super http://www.erightsoft.com/SUPER.html and I like it.

Very raw in feel, but it does a great job and is highly configurable.

Plus it is completely stinkin' free.