The much awaited jQuery 1.5 has released now.Â
This included many performance improvements and bug fixes as well as a major re-write of the Ajax module which now comes with deferred callback management. Core also introduced a new feature called jQuery.sub which allows for new copies of jQuery to be created where properties and methods can be safely modified without affecting the global jQuery object.

Microsoft CDN: http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.5.min.js
Google CDN: https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js