You can easily create that using jquery and iquery easing plugin.
I thnk this – http://www.gmarwaha.com/blog/2007/08/23/lavalamp-for-jquery-lovers/ should help you achieve that effect.
Hope that helps.
You can find the tutorial here :
Edit : Someone Already posted a reply. Didnt refresh the web page before posting.
BTW This site has great Lists for such Jquery Tutorials and Plugins you might find useful : http://www.tripwiremagazine.com/category/tools