The Flash MP3 Player FMP3 is a very small SWF file (only 7 KB) that can be included in HTML or Flash Project to play mp3 files. You can simple modify Object tag to pass the name of the mp3 file, playmode, color and the title of the track. Full commands like play, stop, pause and loop-mode. It's very easy to use.
It's really very customizable; most part of the colors, the title of the music you are going to play, it also displays the elapsed and total time, volume control and a very nice loop button.
Cons
The "play" button, progress bar and volume control bar colors are not customizable. They use an automated google translation from italian to english in their website when they could do a better work and write a translated version themselves.