On the weekend, a new version of jQuery was relesed (1.4.2).  What was already a good library has been optimized and runs even faster.  Those that make heavy use of the library might want to try and upgrade.  And obviously, any new projects should start with the latest version.

http://ajaxian.com/archives/jquery-1-4-2-performance-and-a-few-apis

If you are currently using the 1.3.x version and want to know what’s changed in 1.4.x

http://jquery14.com/day-01/jquery-14