I’m a heavy use of two Microsoft Applications Blocks, namely the Data Access block and the Exception Management block. I haven’t been able to use UI block in any of my projects yet but this new block ‘Authorization and Profile Application’ looks promising. Check out the Microsoft Patterns and Practices home page for a list of very useful resources along with a list of all the Application Blocks.

The Authorization and Profile Application Block is a reusable code component that builds on the capabilities of the Microsoft .NET Framework to help you perform authorization and access profile information.
[Microsoft Download Center]