A cool new technology Microsoft is working on in its Live Labs is called Volta.  It is a way to develop web applications all in one tier, and then late in the development process decide which parts of the code should be client-side and which parts should be server side.  The idea is that you can easily move code fragments back and forth between client-side and server-side at will.  You write your web application in any language of your choice that compiles to .NET and Volta will turn it completely and solely into HTML and JavaScript, meaning your resulting site will be compatible with any browser.  And your site can have all of this with an AJAX look-and-feel.  Check it out here:  http://labs.live.com/volta/

A different Microsoft team is working on a download called ASP.NET 3.5 Extensions (http://www.asp.net/downloads/3.5-extensions/).  It is in "public preview" right now.  It contains some new additions to ASP.NET AJAX, some new Silverlight controls, and a few other cool additions.  Most interesting to me is an MVC Framework  (Model-View-Controller).  One of the managers has a blog that I frequent, and he has written a 5-part series of blogs about this new framework.  This link will send you directly to Part 1 (skipping Part 0):  http://weblogs.asp.net/scottgu/archive/2007/11/13/asp-net-mvc-framework-part-1.aspx

Also, it appears Microsoft recently released a training kit for Visual Studio 2008 and .NET Framework 3.5 available for download now at the following location:  http://www.microsoft.com/downloads/details.aspx?FamilyID=8bdaa836-0bba-4393-94db-6c3c4a0c98a1&DisplayLang=en

Enjoy.