If you get a Windows Mobile 6.5 phone or a software upgrade for your Windows Mobile device, then you’ll notice an icon for Marketplace, the Microsoft Windows Mobile app store. You may have previously come across Windows Mobile Marketplace under the SkyMarket codename (Sky is the usual Microsoft codeword for cloud, while the Microsoft MyPhone service was originally known as SkyBox), but the store didn't officially launch until October 6 with a couple of hundred applications. Marketplace lets you browse, buy, download, and manage applications for Windows Mobile phones (and run each app on up to five phones, so you can take your apps with you when you change phones).

You need to have a Windows Live ID that is associated with a credit card through thewindowsphone.com site unless your mobile operator has signed a deal to let you pay for apps directly through your phone bill (and you’ll need to set that up on the Windows Phone site as well). Greg Sullivan, senior product manager for Microsoft's Windows Mobile division,  said that being able to pay for apps directly through the operator's service is a big advantage. “You do not have to rely on a third-party billing mechanism that may or may not be up to snuff,” Sullivan said.

The first version of Marketplace is only available on phones running Windows Mobile 6.5, but in November Microsoft will release a version of Marketplace that you can install on Windows Mobile 6 and 6.1 phones (by downloading the installer or typing your phone number into a Microsoft Web page to have it sent to your phone via text message).