I never bought or looked into a DVD ripping sofware, but Haruki bought one off the net called #1 dvd ripper. As for what I have heard from him, he said it works perfectly fine. One of my other friend has one called Magic DVD ripper, I am not sure about this one.
Here the site that Haru bought #1 DVD Ripper:
Hope that helps. Frankly, I am not sure if there are any better ones. Hopefully, someone here might know.