CSS-Only Tooltips With Hint.css

Hint.css is a tooltip library that is built with SASS and only uses CSS + HTML. The library uses data attribute, content property, pseudo elements and CSS3 transitions.

qTip2 – Advanced jQuery Tooltip Plugin

qTip2 plugin can display the tooltip in any position wanted, plays nicely with image maps and they can be set to follow any element (handy for drag 'n' dropped and animated items) or mouse.