Microsoft have released the "Enterprise Library" in the patterns and practices web site. This is a revised suite of application blocks that includes the blocks listed below. It looks a much more complete and better integrated product than the previous app blocks and comes with full source code, quick starts, helper configuration applications and unit test. For example, the new version of the Data Access block can use encrypted connection string by taking advantage of the cryptography application block. Certainly worth a look.
Caching Application Block. This application block allows developers to incorporate a local cache in their applications.
Configuration Application Block. This application block allows applications to read and write configuration information.
Data Access Application Block. This application block allows developers to incorporate standard database functionality in their applications.
Cryptography Application Block. This application block allows developers to include encryption and hashing functionality in their applications.
Exception Handling Application Block. This application block allows developers and policy makers to create a consistent strategy for processing exceptions that occur throughout the architectural layers of enterprise applications.
Logging and Instrumentation Application Block. This application block allows developers to incorporate standard logging and instrumentation functionality in their applications.
Security Application Block. This application block allows developers to incorporate security functionality in their applications. Applications can use the application block in a variety of situations, such as authenticating and authorizing users against a database, retrieving role and profile information, and caching user profile information.
Details here: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html/entlib.asp