In the lead-up to Apple reaching its milestone of 10 billion downloads in the App Store, the company has revealed its all-time top free iPhone Apps.

At the top of the list is social networking app Facebook. Streaming music app Pandora Radio is in second place and the Google Mobile App comes in third place.

In total there are three apps in the social networking category and two in the music category in Apple's top ten.

The rest of the top ten apps are divided evenly between the reference, entertainment, weather, travel and games categories.

Apple's All-Time Top Free iPhone Apps in the US App Store:

  1. Facebook - Social Networking -
  2. Pandora Radio - Music -
  3. Google Mobile App - Reference -
  4. Shazam - Music -
  5. Movies by Flixter - Entertainment -
  6. The Weather Channel - Weather -
  7. Google Earth - Travel -
  8. Bump - Social networking -
  9. Skype - Social Networking -
  10. Paper Toss - Games -