Another great thing about jQuery is the plugins available. There are literally hundreds of free, open-source (just as jQuery itself is) plugins that build on jQuery’s capabilities.
One I just discovered is called “Ajax Fancy Captcha“, which gives you a really unique and fun CAPTCHA (which is the anti-spam method you see on many web forms). It’s still being developed and improved, but it’s a great idea. Other jQuery plugins include Cycle for slide shows and Step Carousel for image carousels, Lightbox, and Shadowbox.