First you need to get the DVD ripped to a format you can edit. For this step you can use DVDx (free): http://sourceforge.net/projects/dvdx/
I haven't used it myself so I can't give you step-by-step instructions but if you search for "dvdx tutorial" or "dvdx walk through" you should be able to find that. You can also find other options for this step by searching for "dvd to avi".
Once you have the DVD ripped to a format like AVI that you can edit, you can use Window Movie Maker (should be a free program that came with Windows, more info here: http://www.microsoft.com/windowsxp/using/moviemaker/default.mspx
) to edit the video. Once you get to this step if you have any problems feel free to ask, I can poke around in the software and see if I can figure out the answer.
Now you should have your edited video, and the last step is posting it online. The best format for online video is .flv, which is Flash video like on Youtube or MySpace video etc. The easiest way to do this step is to just upload it to a video sharing site, as they'll do the conversion for you and you'll then have a hosted video. Here are three recommendations for this:
1) Youtube: The advantage here is that this is by far the largest video site on the internet.
2) MySpace Video: The advantage here would be if you already use MySpace as a marketing tool.
3) Vimeo: The advantage here is higher quality video.