The number of available applications for Microsoft’s mobile platform now totals more than 30,000, according to the blog Windows Phone Applist, which tracks Windows Phone 7 apps. Apple’s App Store counts 425,000 apps, while Google has about 250,000 Android apps, according to unofficial tallies.

Microsoft needs to continue to build its app count if it hopes to catch its rivals in the smartphone market. Between Windows Mobile and Windows Phone 7, the company commands less than 6% of the total U.S. mobile OS market, according to the latest numbers from Comscore. Google’s share now tops 40%, while Apple’s stake stands at almost 27%.

Microsoft is hoping that the release of the Mango update later this year will boost its numbers. Mango adds more than 500 new features. Many are backend services that will be transparent to the end user, but others, such as multitasking and hardware assisted Web browsing through Internet Explorer 9, will yield noticeable improvements.

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Microsoft last week said it had started stocking its App Hub for Windows Phone 7 with applications that can take advantage of capabilities built into the Mango update.

“This means that new and existing titles optimized for Mango features like fast app switching, background audio, multiple and double-sided Live Tiles, better Search integration, and more will begin publishing in a matter of days,” said Todd Brix, Microsoft’s senior director for Windows Phone marketplace, in a blog post.

Brix said Windows Phone users who are running a pre-release version of Mango will be able to download and run the new apps almost immediately, but general consumers will have to wait until Mango is made officially available. Brix did not specify a release date, but most observers believe the Mango update will drop sometime in the fall.