With the release of the RTM version of the Windows Phone 7 developer tools set for the 16th of September. This series of 12 screen casts from Microsoft MVP'S Andy Wigley and Rob Miles is a seriously good way to get up to speed in developing applications with Silverlight and XNA for the Windows Phone 7 Platform. Aside from the bad jokes and the English Accents both these guys have years of experience developing for the mobile platform and their enthusiasm and excitement about the Windows Phone 7 Platform shines through.
See the first Screencast here which has the links to the other 11:
Windows Phone 7 Jumpstart Introduction
You can also get the code examples and accompanying documents here at the Jump Start Site:
Jumpstart Companion Site