Loud links is a simple tiny Javascript library to add interaction sounds to your website. The library creates HTML5 audio element and uses it to play mp3/ogg audio files which is currently supported in all browsers.
Microm is a beautiful library to convert browser microphone to mp3 in Javascript.
Microm goal it's to make trivial to play and convert audio in the browser.
Ion.Sound is a jQuery plugin for playing sounds on events. Ion.Sound is afreeto use and has cross-browser support. It includes 15 free sounds.