Dragon NaturallySpeaking (not free):

• can do voice transcription, but only on a single voice (i.e. not designed for use with multiple speakers) and this voice has to be yours as you need to train Dragon before him.
• recognizes .wav, .wma, .dss, ds2 and .mp3 files for the PC version (.wav, .m4a, .m4v, .mp4, .aif, and .aiff audio file formats for the Mac version)
• can be taught new words and be trained to improve the accuracy.

Dragon NaturallySpeaking (not free):

• can do voice transcription, but only on a single voice (i.e. not designed for use with multiple speakers) and this voice has to be yours as you need to train Dragon beforehand.
• recognizes .wav, .wma, .dss, ds2 and .mp3 files for the PC version (.wav, .m4a, .m4v, .mp4, .aif, and .aiff audio file formats for the Mac version)
• can be taught new words and be trained to improve the accuracy.