A few good ones to consider are:
I'm not sure if they all do audio, but some do at least. I've used Flowplayer myself.
These scripts only handle video or audio, respectively, but I just can't leave without noting them:
[Video.js and [url=http://kolber.github.com/audiojs/]audio.js](http://videojs.com/)
Nice links, sdleihssirhc.