.NET Application Blocks are distinct pieces of code, created by the Microsoft Patterns and Practices Team (PAG), that demonstrate the best practices on how to accomplish a specific task using .NET. They are ready made code that you can use/extend to make your lives a WHOLE lot simpler.

I like them as they are extensively tested and reviewed (which hopefully minimizes security issues).

I noted earlier that the PAG had released a new App Block.

Here is a complete list of the App Blocks [1] and where you can download them. I will keep the list up to date as new ones are released.

[1] http://CyberForge.com/weblog/aniltj/articles/217.aspx