The new Windows Phone 7 Series was announced in February, replacing Windows Mobile 6.5 and revealing a brand new user interface developed by Microsoft. Today during MIX10, Microsoft focused on the developer side of the new platform and made several new announcements about the device. One of the biggest was the release of the new developer tools that are needed to make applications. Microsoft also revealed it’s plans for the Windows Phone Marketplace and presented a huge list of partners already working on applications, including Netflix, Sling, Foursquare, Pandora, PopCap Games, and many more.

To make a successful smartphone these days you need a large collection of software to run on the device. You also need a destination that users can go to download the software. This is what the new Windows Phone Marketplace is for, but it won’t just offer applications, it will also have music available to buy. With the store in place, the next step is to offer developers a way to create and publish applications. The new Windows Phone Developer Tools are available as a free download for developers starting today. In the package is a copy of Visual Studio 2010 Express for Windows Phone and XNA Game Studio. These should give developers the tools needed to begin writing applications that make full use of the new platform.

Microsoft also let some third-party developers show off the applications they have been working on for the Windows Phone 7 Series. The big star of the show was Netflix, who showed off their Silverlight powered video rental application. They even include the Watch Instantly feature, allowing the user to stream videos directly to their phone. This is the first time Netflix has offered this on a phone. Other developers showed off all sorts of applications, including games which use XNA to bring the Xbox experience to the phone. It seems that Microsoft has done their homework and are hoping to offer large collection of applications when Windows Phone 7 Series launches later this year.