WordPress tooltip lets you easily add css tooltips to content on your posts and pages.
This plugin is largely based on isharis's plugin: "WordPress Tooltip" which uses the TipTip jQuery plugin. Many thanks Muhammad! Note that I've corrected the main bug which prevented it from working in some server configurations (tinyMCE form just redirected to the site homepage).
It uses the excellent "Sexy Tooltips with Just CSS" authored by Alexander Dawson (http://sixrevisions.com/css/css-only-tooltips/).