There are numerous JavaScript libraries that are worth at least a cursory review to see if they suit your particular need. First, come up with a short list of criteria to guide your selection and evaluation process.
Then, check out a high level framework comparison/reviews somewhere like Wikipedia, select a few that fit your criteria and interest you. Test them out to see how they work for you. Most, if not all, of these libraries have websites w/ reference documentation and user group type support.
To put some names out there, Prototype, script.aculo.us, Jquery, Dojo, YUI...those all seem to have active users and contributers, so they are probably worth reading up on to see if they meet your needs.
Jquery is good, but with a little extra effort, maybe you'll find that something else works better for you.
Good luck.
