New version of Microsoft Solutions Framework (with Agile twist).....
Technically, there are now two models for MSF - formal and agile.
Oh, and one cannot forget Visual Studio Team System (something I've been drooling over for months now). All I can say is, software development life cycle tools for .NET development have fully arrived.
Anyway, exciting stuff coming out that I think will have as big an impact on development teams as any feature added to VB/C#, VS.NET, etc.