This cheet sheet attempts to better align with the new documentation structure jQuery is now using and clearly marks all new and updated functions for jQuery 1.4
First off, please do not link to the file directly, or put the file on your own server. If you would like to distribute the cheat sheet please link to this post.
With this much content on one page I am bound to have made a mistake or two. If you see any errors please drop me a comment and I will try to get it fixed up as soon as possible.