Microsoft’s Windows Phone Marketplace has now reached 40,000 applications.

The rate of growth has accelerated since late October, when Microsoft hit 35,000 apps, to push the Marketplace onto 40,000 apps. All About Windows Phone reports that their own tracking software indicates 40,189 items have been published to the Marketplace. 10,882 apps were added in the last 90 days and 4,770 were added in the last 30 days alone. The apps come from over 10,000 publishers. The site estimates that the Marketplace will reach the 50,000 app mark by January 2012.

WP7applist, a rival tracking site, is currently reporting 38,641 applications worldwide and explains 5,429 of them are inactive, 53% are available for free and the average price is $1.72 per paid application. Microsoft’s Windows Phone Marketplace is growing at a steady rate. The Marketplace passed 15,000 apps in April just in time for its six month birthday and reached 35,000 apps in October to mark a year of Windows Phone. WP7applist says that 197 apps are updated on average each day. In the last 24 hours, 140 apps were updated and 149 were added.

Windows Phone 7 launched on October 21 with 1,000 applications available in its first week on the market. A year later and the Marketplace is growing with 40,000 apps. Microsoft appears to be building up a good momentum amongst application developers. Microsoft recently finalized its Windows Phone 7.5 “Mango” update and has distributed it to 100% of existing eligble devices. Microsoft’s device partners have also started to release a number of new Windows Phone 7.5 devices for the holiday season, including the HTC Radar, HTC TITAN and Samsung Focus S.

Nokia’s Lumia 800 device went on sale across the UK and some parts of Europe on Wednesday. Orange UK reported strong preorders of the device, surpassing records for previous Nokia preorders. A number of stores in the UK opened early on Wednesday for potential customers. Nokia representatives handed out free chocolate and coffee to potential customers on London’s Oxford Street on Wednesday. Nokia’s Lumia 800 is available on a range of contracts and carriers in the UK, starting at £26 per month.