Not an earth shattering-shattering optimization, but I thought I'd throw this out there - Use CDN's for jqueryjQuery, etc..
Quote from ScottGu himself: The Microsoft Ajax CDNCDN enables you to significantly improve the performance of ASP.NET Web Forms and ASP.NET MVC applications that use ASP.NET AJAX or jQuery. TheThe service is available for free, does not require any registration, and can be used for both commercial and non-commercial purposes.
We even use the CDN for our webparts in Moss that use jqueryjQuery.