Android's App Market isn't as large as the App Store, but it is getting there-fast! BGR reports that the App Market may have just exceeded 50,000 applications. At Google's Q1 earnings call, they reported 38,000 applications. That was a month ago, and the last month saw over 9,000 new apps added (via AndroLib).
While Google hasn't officially confirmed these numbers, there's no doubting that they are 'in the ball park'. The App Market isn't far from Apple now. When Android can brag an equal number of apps, they'll have a powerful advertising tool against Apple.