Microsoft Visual Studio 2010 and .NET Framework 4.0 Community Technology Preview (CTP) has been made available for download (as of 26 Oct 2008). You can get the latest bits here.
It is about a 7.5 GB download so be prepared for it to take a little while, especially since it was just released.
There is a ton of new functionality in VSTS 2010, far too much to enumerate in this post. However, you can check this previous post of mine as a starting point for getting more details.
Download VSTS 2010 .NET 4.0 CTP