Microsoft has recently released the Silverlight Toolkit. 

What is the Silverlight Toolkit?

The Silverlight Toolkit is a collection of Silverlight controls, components and utilities made available outside the normal Silverlight release cycle. It adds new functionality quickly for designers and developers, and provides the community an efficient way to help shape product development by contributing ideas and bug reports. This first release includes full source code, unit tests, samples and documentation for 12 new controls covering charting, styling, layout, and user input.

 You can download this set HERE.