Kik Messenger or GoWalla. and even some exclusives like AmazonFresh. It's been less than a year since the WP7 introduction, and we are now at the 25 000 mark, with the last 5000 taking only a month or so.
Granted, the developer's attention got focused towards WP7 when the news about Nokia Windows Phones broke, but still, Microsoft now boasts 40 000 registered developers and 100 apps submitted daily. With that tempo, when Nokia Sea Ray hits in the fall, the Marketplace might have passed the 40 000 mark.