Todd Brix, Senior Director of Windows Phone Division, posted in the Windows Phone Developer Blog that the Marketplace is now accepting and certifying Mango apps!

These apps can take advantage of new Mango features such as fast app switching, background audio, multiple and double sided Live Tiles, better Search integration and more.  WP7 currently has over 30,000 apps (in less than a year since the OS was launched) and developers can now optimize their apps to truly take advantage of Mango.

Todd Brix does mention that although this does not signify an early release of RTM mango, it does mean that anyone running a beta version of Mango will be able to see and use these apps.  Check out some awesome features developers can now utilize:

*The WP SDK 7.1 RC (Release Candidate) tools, available in English and Japanese, include the ‘Go Live’ license that lets developers publish their apps to Windows Phone Marketplace

*Developers should submit their apps now to become a part of the must-have app selection in time for the new wave of Mango phones coming this Fall

*Game developers can now submit games to the 19 new Mango markets announced in in July, including: Brazil, Chile, Colombia, Czech Republic, Denmark, Finland, Greece, Hungary, India, Japan, Netherlands, Norway, Poland, Portugal, Russia, South Africa, South Korea, Sweden and Taiwan

*The new WP SDK 7.1 RC accelerates app time to market:

 *The WP SDK 7.1 RC includes the completed Marketplace Test Kit that allows developers to test their apps for certification requirements before submitting to Marketplace, ultimately speeding up the app certification process and the time it takes an app to hit Marketplace

*Developers can easily cross submit games and ratings information to multiple markets via App Hub

 *For those developers interested in making money with in-app advertising, the Microsoft Advertising SDK for Windows Phone is now installed as part of the WP SDK 7.1 RC tools, making it easier for devs to get started monetizing their apps

We put out an article yesterday going over Brandon Watson’s efforts to capture WebOS developers and his general attitude towards welcoming all developers with open arms ready to help in any way he can.  Armed with these tools and with seemingly endless resources from Microsoft, developing for WP7 sounds like a great idea (I’m sure MS would agree).

So what are you waiting for?  Start developing Mango apps!