Programming Windows Phone 7 – by Charles Petzold
Windows Phone blue book – by Rob Miles
Silverlight for Windows Phone – by Puja Pramudya
Beginning Windows Phone 7 Development – by Henry Lee and Eugene Chuvyrov
Microsoft Silverlight Edition: Programming Windows Phone 7 – by Charles Petzold
Persons that tweet about WP7
Please let me know if you have any great WP7 development resources.