Using a new and Free application, now you can build your own Windows Phone 7 apps using AppMakr
For the cost of nothing more then registering with AppMakr, you'll have everything you need to get started building apps and publishing them to the Windows Phone 7 AppStore. Without ever writing one line of code you'll be able to create mocks of your app, prototype them and get them to Market for Free. And while some feature tools by 3rd party authors may have a fee, the basic tools are included with AppMakr.
and start building Apps.