You can download Enterprise Library 4.0 for Visual Studio 2008 and the .NET 3.5 Framework. Unity IoC Integration is the big change, so expect a few tutorials and screencasts on it as well as on the changes to the existing application blocks.
Those new to Enterprise Library can look at the following post on my personal site for a few introductory tutorials on the Application Blocks. That is where most of my Enterprise Library Tutorials reside.
Download Enterprise Library 4.0 here.
Enjoy!