Sitefinity supports the following types of controls:

1. Built-in Sitefinity controls (such as Blog Posts, News, Events), Field Controls, Sitefinity Specific Controls
2. Standard ASP.NET controls (such as HyperLink, Label, GridView, XmlDataSource)
3. ASP.NET User Controls (Custom Developed user controls that developers can include in the Sitefinity toolbox). More information about user controls is available on MSDN.
4. ASP.NET Web Server Controls (Custom developed controls that developers can include in the Sitefinity toolbox) . More information about ASP.NET Custom Controls is available on MSDN.
5. Module Controls (Controls from custom modules that represent the module's frontend functionality)

6. Telerik RadControls for ASP.NET AJAX - The award winning Telerik RadControls for ASP.NET AJAX are coming with Sitefinity, so you can use in your own Sitefinity projects.

   NOTE: The RadControls coming with the CMS can be used only within the context of the application. You will get a trial message if you use them in separate projects.

7. Telerik RadControls for Silverlight - You can also use Telerik RadControls for Silverlight by properly wrapping them in an ASP.NET control.

NOTE: When developing controls for Sitefinity (be they User Controls or Custom Controls), there are NO special requirements imposed by Sitefinity. It is possible to use controls created for other systems by simply including them to the Sitefinity toolbox.

Sitefinity also provides Control Designers for some of the Built-in Module controls. The designers could be extended to cover custom controls as well.