Windows Mobile Marketplace, announced at the Mobile World Congress in Barcelona by Steve Ballmer, is opening the doors for developers as promised. The Windows Mobile Team announced it on their blog as follows:

In the latest update to http://developer.windowsmobile.com, developers can now Register to participate in Windows Marketplace for Mobile. This marks another milestone in providing Windows Mobile Developers a clear path to develop, test, certify and distribute their Windows Mobile applications via the Windows® Marketplace for Mobile.

Microsoft plans to charge developers $99 a year, plus $99 per application, to submit applications to Windows Marketplace for Mobile, though this year, developers are being allowed to submit up to five applications free of charge for that $99 yearly fee. Developers will receive 70% of the net price of the application (not including taxes) that Microsoft collects when your application is purchased.

So what are the steps for developers?

· REGISTER NOW. Developers can submit their complete profile information and take the first step in registration.

· Follow the Windows Mobile Developer team on Twitter @wmdev, Facebook and YouTube.

· Keep up to date via the Windows Mobile Team blog.

· And, stay informed with the latest development tools on the Windows Mobile Developer Center on MSDN.

And, if after reading the FAQ, you still have questions for the team you can comment on their post. According to the comments there are some problems with the registration, like the payment step repeatedly failing and international users being blocked. Apparently you may only sign up if you are in the US, as the credit card address entry automatically fills in "USA" as country which you cannot alter. However there is no mention at all of the registering only being open to US residents on either the blog or the FAQ! Hopefully these issues will be solved soon.

Previously (at CTIA) Microsoft announced that they have already signed up 27 big name-partners for their mobile Marketplace, including Facebook, Sling, EA, AP and CNBC. Want to know what the Windows Mobile Marketplace will look like? Head on over to Geoffrey Emery's for some screenshots, or to Long Zheng’s for the promotional video.