HandBrake is an open-source, GPL-licensed, multiplatform, multithreaded video transcoder, available for MacOS X, Linux and Windows.
Handbrake is a good DVD ripper, current version will rip to mp4 and mkv, older versions will rip to avi also. When used in combination with DVD43 it is useful for ripping DVDs with DRM(digital rights management)
Great for converting videos for iPad etc…