The video below is a nice level 200 video recorded at TechEd 2010 Australia showing you a basic intro with develop applications with Silverlight for Windows Phone 7.

Source http://www.msteched.com/2010/Australia/DEV252

Here is good video showing how the application market place is used on Windows Phone 7. It show some really nice transistions between screens and how you add a application to your home screen. Also interesting to note is the the “Contoso” options on the Market Place home screen which could be how enterprises and carriers could distribute applications.

CNET just posted a video of Charlie Kindel from Microsoft demoing some games and apps on Windows Phone 7.

Home Screen