Microsoft has begun accepting submissions for its Windows Marketplace for Mobile, the next big step in the company's attempt to challenge Apple's App Store for the iPhone. Todd Brix, a Microsoft senior product marketing manager, announced the news and contrasted Microsoft with Apple by promising to provide clear guidelines and feedback to the developers that submit apps for Windows phones.

The company also announced a developer contest designed to stir new interest among mobile-phone software developers.

"Our strategy for all of this is pretty straightforward; we want to create a global marketplace for Windows Phones where developers and users meet to sell and buy high quality and high value applications that make work easier and life more fulfilling," Brix wrote in a blog post this afternoon. "We’re creating a clear process and new opportunity for developers and ISVs to make money from their investment in innovation. The applications we feature will be well organized, easily accessible by PC or phone and backed by a money back guarantee. And when they’re ready to buy, customers will have a variety of payment options to choose from. These are new customer experiences, and frankly, capabilities that will set us apart."

Apple has been criticized for not being clear enough with developers who submit apps for consideration for the App Store. However, that hasn't kept Apple from building momentum for the iPhone and iPod tough by attracting a large volume of third-party applications.

Attempting to get the attention of developers, the company also announced a "Race to Market Challenge" contest today. Winners will be chosen based on criteria including most downloads of a free app, most valuable app (downloads x price), most useful app and most playful app, the latter two as judged by a Microsoft panel. The contest runs from the Mobile Marketplace launch in the fall to the end of the year.

Winners will receive a developer edition Microsoft Surface table in addition to online marketing and promotion.