Jesse Liberty, Senior Community Program Manager for Microsoft, is publishing a series of tutorials on porting applications from the iPhone to Windows Phone 7.
His tutorial covers the basics of getting started, from hardware to software to registering with marketplace. He also covers some misconceptions some developers may have about moving software to Windows Phone 7, such as performance issues due to non-native development (not a problem it turns out).
He also covers the differences and similarities between the languages and resources used, and generally makes it easy for developers disappointed by poor sales on iOS (the majority) to get familiar with the new operating system and try their luck by getting in on the ground floor of the new platform.
See the first part of the tutorial here.