This plays streaming music from soma.fm and (optionally) scrobbles track information to last.fm.
somafm -h
This depends on mplayer (brew install mplayer) to play the somafm channel.
This just plays audio files that you have in a local directory and (optionally) scrobbles track information to last.fm.
play_music -h
This depends on ffmpeg (brew install ffmpeg) to extract id3 tags.
You need to create your own api key on last.fm to be able to perform scrobbling - the sign up is here. Once you have this, you will be able to enter the key, secret and then authenticate as a last.fm user.