I think the coolest thing about jQuery is that people are writing plugins. This is extremely useful when you are just trying to get something done and there is just a plugin you can use that does what you want to do.
Simple plugins like the DOM Element Creator plugin are just the sort of things that are amazing. Anything that I can use that just makes DOM manipulation easier is much appreciated.
The other thing that is pretty nifty is the jQuery UI stuff that they have going. Definitely check out the demos, there is some cool stuff, especially the carousel they have for the available demos. Just check it out. Pretty impressive.