Nice thread. My first contribution, for those ASP.Net developers that want controls AND the jQuery UI...
Dot Net JQuery
DNJ is a .NET framework that provide advanced AJAX WebControls and features :
* Ajax extender : Ajaxify your existing .Net controls like the ASP.Net UpdatePanel does, but in a more customisable way
* Advanced pure AJAX WebControls : DNJ integrates all jQuery UI widgets in Visual studio toolbox and allow you to customise them in VS designer.
Please visit http://www.codeproject.com/KB/aspnet/dotnetjquery.aspx for quick documentation