Wouldn’t it be cool if you could easily manipulate HTML elements onscreen? Wouldn’t it be nice if AJAX requests could be sent with only one line of code? Take a look at Script.aculo.us.
What is Script.aculo.us? It’s a set of JavaScript files (based off the Prototype JavaScript library) that lets you do numerous cool and/or useful things with ease. Fading, sizing, and movement actions are only a couple lines of JavaScript away. Not to mention easier AJAX techniques.