Google is celebrating the 10 billionth app download from the Android Market with a "10 Billion Promo" that offers 10 apps for $0.10 each, or 10p in the UK. There are some great apps too: SwiftKey X, Minecraft, and SoundHound, to name a few. SwiftKey X is a popular replacement for the stock Android keyboard, and SoundHound can identify songs much in the same way as Shazam does. Minecraft, on the other hand, needs no introduction. Google's banner ad indicates there'll be 10 days of offers, so we'd expect another good deal tomorrow.