There are some really great stuff in this resource kit that can be downloaded from MSDN.
While the .NET Resource Kit is targeted at VB programmers, it comes with tons of real 3rd party controls for free that work just as well for C# programmers as well as VB.NET programmers.
Here are two extracts from the introductory letter on the resource kit by Chris Dias (Group Program Manager, Visual Basic Product Team).
The information on the Visual Basic .NET Resource Kit CD is organized by common development task: Windows programming, Web and XML Web services programming, mobile device programming, and data access. Each of these major categories is further organized by several common subcategories, including Conceptual Overviews, Code Samples, Step-by-Step Walkthroughs and Quick Start Guides, Training and Certification, Best Practices Sample Applications, Recommended Reading, and Sample Book Chapters.
The CD also contains an impressive collection of free .NET controls from leading control vendors such as ComponentOne, Dundas, Infragistics, SAX software, and others. Building and distributing your applications using these controls will dramatically reduce your development time.