John have just announced jQuery 1.2.6, a bugfixes releases with major improvements and many new features. Key performance improvements include 103% Faster Event Handling, 13% faster CSS selectors, 21% faster .offset() and 25% faster .css(). New features and major changes in jQuery 1.2.6 :

• The Dimension plugin by Brandon Aaron is now part of the jQuery core.
• .attr() method has been completely overhauled
• .toggle() can now accept more functions
• .unbind bound .toggle() and .one() functions
• .index() supports jQuery collections
• jQuery.makeArray can convert ANYTHING to an array.
• beforeSend can cancel Ajax calls
• Exposed Speeds

More information and download from jQuery.com