There is for sure now an app for that.
During last night the Apple iTunes App Store received its 500,000 app. It is actually not Apple touting that milestone, but three mobile app related companies: 148apps, Chomp and Cillingo. The three companies pulled together for a nice PR move publishing a huge infographic on Facebook marking the 500,000 apps milestone. I am not sure if Apple is too pleased that other companies ride this milestone, but the iTunes store is accessible to everyone and everyone can count the approved apps.
As CNN Money notes right now there are only about 400,000 apps available for download. About 100,000 have been withdrawn, replaced or removed for other reasons.
The 500,000 apps milestone will be sure celebrated again at the WWDC 2011 keynote.
To see the infographics celebrating the 500,000 apps milestone visit this Facebook page. It features a nice history time-line visualizing the growth of the iTunes app store. Apple launched the iTunes App Store in July of 2008.