If you haven't heard already, VS.NET 2008 beta 2 is now available for downloading.  I'm installing it right now. :-)

http://www.microsoft.com/downloads/results.aspx?DisplayLang=en&nr=20&freetext=visual+studio+2008&sortCriteria=date

Make you sure read Scott Guthrie's blog after the installation.  He links to a batch file that needs to be installed afterwards to fix some policy issues on the System.Web.Extensions.dll assembly.

http://weblogs.asp.net/scottgu/archive/2007/07/26/vs-2008-and-net-3-5-beta-2-released.aspx