here are a few such sites :
http://www.w3schools.com/
js/default.asp
http://www.echoecho.com/javascript.htm
http://www.webteacher.com/javascript/
http://www.webdeveloper.com/javascript/javascript_js_tutorial.html
http://www.howtocreate.co.uk/tutorials/javascript/
http://www.tizag.com/javascriptT/
cheers and happy learning!