It is not the release version of the Enterprise Library yet but a Community Technology Preview release. Anyway, a lot of .NET 2.0 developers are waiting for this release. And as SharePoint SP2 will bring SharePoint developers also to the 2.0 version of .NET, they should also have this in their downloads folder :-)
What is it?
The patterns & practices Enterprise Library is a library of application blocks designed to assist developers with common enterprise development challenges. Application blocks are a type of guidance, provided as source code that can be used "as is," extended, or modified by developers to use on enterprise development projects. Enterprise Library features new and updated versions of application blocks that were previously available as stand-alone application blocks. All Enterprise Library application blocks have been updated with a particular focus on consistency, extensibility, ease of use, and integration.
Join this workspace and download it from the downloads section. (There seem to be some problems at the moment of writing to get the actual download)