So, the Windows 7 Phone tools are out for everybody to start developing your apps. Here's the link to the developer portal: http://developer.windowsphone.com/ I would like to direct your attention to the following documents, before you start playing with the bits: Windows Phone UI Design...

You've probably heard about the announcements made at the MIX08 about the Silverlight on Windows Mobile devices. Check out this great presentation that was done by Amit Chopra and David Kline on the roadmap, tips and tricks of developing pages for devices etc...