Give this media converter a try too. It is freeware and an opensource project on sourceforge. It handles most all of the video and audo types you could want and they are making it better all the time. Some commercial apps like intervideo have a more wiz-bang interface though.

Quoted: MediaCoder is a free universal audio/video batch transcoder, putting together lots of excellent audio/video codecs and tools from the open source community into an all-in-one solution, capable of transcoding among different audio/video formats with many extra features.