If your looking to steam an audio on the web, .wma is the way to go. it can be converted down to 24kbs 56 is decent since the majority of people probably use broadband anyway. but just incase there are dial up users, 56 or so wont be too bad of a stream. Lots of programs out there that convert MP3 to wma or wav... google mp3 to wave ect.
WMA but WAV pending on Kbps rate. Mp3 is a moderate size file type but they have tons of file compressors for all types of files so find one for music.Try 5 star shareware.com or google it.