The jQuery plugin clueTip looked like a promising jQuery plugin for showing advanced tooltips via AJAX. However, it has an issue when run in the Google Chrome browser (build: 11.0.696.68).
This was discovered when I tried out the basic ajax option at the clueTip Demo.
Example of the issue is at: http://c9.io/finneycanhelp/html5fun2/workspace/MouseOverQTipAjax.html where I get a 404 error.
Another example is when I try it locally with the same code and I get a: Origin null is not allowed by Access-Control-Allow-Origin.
Some Good News:
It works as expected in Firefox and IE 8. Perhaps that is sufficient for what you may need.
I look forward to when this Chrome specific issue is fixed in later versions of clueTip! The plugin is neat!