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.
The cheat sheet comes in two flavors:
Made for iPhone and iPod Touch, and any other mobile device with internet access: http://labs.colorcharge.com/jtouch. Read about its release on the blog entry.
Old-school printable A4 cheat sheet: 
JQuery is © of John Resig and the jQuery team.