I've used the html audio tag, 'cause I am lazy older browsers will not see players in the map pin info bubbles .
Update 2011-06-25 doing a bit of feature detection and using a flash player for browsers that can't do html5 audio for mp3s. Using imlucas's gist: 341559 — Gist & jQuery.
This webpage just puts my boos on the map using the rss feed from audioboo, php to parse it using XMLParser Documentation/Tutorial google map info and code from info from Google Maps API Tutorial.
I also borrowed some css from ZURB – Super Awesome Buttons with CSS3 and RGBA and mades the shadows for the map icons with Shadowmaker.
iPad woes, I can't seem to get the audio player to work in the gMaps ballons, work ok here: