I recently published a new screencast on Channel 9 entitled “Introduction to Multitouch Development in Silverlight” at https://channel9.msdn.com/posts/Introduction-to-Multitouch-Development-in-Silverlight. It’s a quick (5-minute) introduction to multitouch development in Silverlight. I briefly discuss the major differences between multitouch development in Silverlight and WPF, and then demonstrate a Silverlight multitouch code sample where an "Ouch" will appear wherever your finger touches the screen.
The code is available for download here. Ping me with any questions.