Wow today at the PDC they announced the beta release of Siverlight 4.  I could feel something big was coming and I was not let down.  Here is a brief overview of the new features of Silverlight 4. 

1. Tooling support for Silverlight 4 has been incorporated into Visual Studio 2010.  I still believe that blend plays a strong role in developing Silverlight application, but these changes are nice to see. 
2. RIA or WCF Services has been added into Visual Studo 2010.
3. Printing API
1. You create a PrintDocument Object and assign UIElements to the PageVIsual section and they will be printed.  Keep in mind you can generate your own you own UI just for printing.
4. Full Right Click support this is great think about using it with an existing asp.net application to hide the default menu.
5. Web CAM and Microphone support. nuff said.
6. MouseWheel support
7. RichTextArea Control
8. ICommand support
9. Clipboard API yes you too can use the clipboard.
10. HTML hosting control
11. Elevated Trust
1. Give access to the file system and making web calls without needing a client access policy file on the server.  This can only be used for Silverlight OOB application.
2. COM Interop
3. Access tot he notification area
12. You can use the Network Credentail information with ClientHttp requests.
13. Full keyboard access in Full Screen mode
14. Text Trimming
15. Silverlight now acts as a Drop Target
16. Binding to Dependancy objects.  String Format in bindings (no string converters).
1. TargetNull and Fallback value
17. MEF Support
18. DataGrid improvement
19. Google Chrome support