According to third-party Windows Phone 7 Marketplace monitor WP7applist, Microsoft’s mobile application store is now home to over 4,000 applications. The site, which provides a Web-based interface for searching and browsing Windows Phone 7 apps, shows a current app total of 4,005. Microsoft announced on November 25th that its mobile app market was home to 3,000 apps, so the 4,000-app milestone comes 20 days later. The pace has slowed slightly compared to Microsoft’s jump from 2,000 apps to 3,000, which took just 17 days, but the rate new apps are hitting the Marketplace is still impressive. At its current pace, the number of apps in the Windows Phone 7 Marketplace will surpass the Palm App Catalog some time in the first quarter next year. Palm’s App Catalog launched in June of 2009, and currently offers approximately 5,800 apps.