It appears that the Google Android operating system is growing into a real contender with the growth of its marketplace for apps having now broken through the 20,000 apps level.

While Google does not provide any official accounting of how many applications are in the Android Market, Web site AndroLib keeps track of the number of both paid and free apps in the store.  According to the site’s tracking, the Android Market passed the 20,000 app mark sometime on Monday afternoon.

The number of applications doubled in the past five months from 10,000, showing that interest in the platform definitely seems to be growing.  2010 is expected to be a big year for the operating system with numerous new phones being released, including the NexusOne.

Of interesting note is that it currently looks like nearly 63 percent of the applications are free ones, meaning that the majority of them are probably ad supported.  If the Android Marketplace continues to grow like this, it could mean good things for advertising networks as well as the platform itself.