jQuery is around for a while already, but only recently I actually sat down and decided to give it a go. jQuery website defines itself as:

jQuery is a fast, concise, JavaScript Library that simplifies how you traverse HTML documents, handle events, perform animations, and add Ajax interactions to your web pages. jQuery is designed to change the way that you write JavaScript.

After trying it out, going through jQuery wiki pages I have to say it probably is the best Javascript framework I’ve seen. I have tried mootools (not very recent though), scriptaculous, but jQuery just beats them all. It’s lightweight, very easy to use, has a bunch of ready-made plugins and a large community.

If you’re planning to do some Javascript, try jQuery. Meanwhile I am placing jQuery on my must-use list.