SoundManager 2 : Using HTML5 and Flash, SoundManager 2 provides reliable cross-platform audio under a single JavaScript API.
Parsley.js : Javascript forms validation.
Powerful, UX aware & Dead simple.
The HTML5 Shiv : The HTML5 Shiv enables use of HTML5 sectioning elements in legacy Internet Explorer and provides basic HTML5 styling for Internet Explorer 6-9, Safari...
HTML5Forms.js is a JavaScript polyfill that implements a subset of the HTML5
Forms module in all browsers. The script will only add support for the
different parts of the module when there doesn't exist a native
implementation.