jQuery is ( my opinion ) one of the best things to hit the web development scene.. you can accomplish anything with it from games, awesome web apps, or just simply awesome Web stuff. the community is huge and there are some awesome plugins out there. I have a collection of different plugins that are really usefull. I am including my favorites ones, but will Post more bit later. I am also including a great CSS link. enjoy!
Simple jQuery slideshow Plugin : http://slidesjs.com/
Super-smooth Transitions : http://ricostacruz.com/jquery.transit/
CSS3 Animations : http://daneden.me/animate/
Stroll.js : http://lab.hakim.se/scroll-effects/
jRumble : http://jackrugile.com/jrumble/