Overview
This Web Part allows SilverLight Applications to execute inside of a Web Part. The Web Part can be configured to specify the SilverLight application, its initialization parameters and Alternate HTML when the plugin is not installed.
You can see this Web Part on the SharePointHQ site here and here and here.
Screenshots

The configuration tool pane allows specifying the SilverLight application, initialization parameters, the minimum version to support and the HTML to show when the SilverLight plugin is not installed.
A sample of what the Alternate HTML can look like when the Plugin is not installed.
Known Limitations
- This Web Part requires SilverLight 2.0 and 2.0 SDK to be installed
- This Web Part requires AJAX to be enabled
- This Web Part requrres SilverLight to be configured in IIS
Live Preview of Web Part