To think, it's only been three months since we talked about Apple's iTunes store crossing the 500 million download threshold, and now it looks like the gang in Cupertino are gearing up to celebrate their 1 billionth app. To celebrate, the company's released two lists showcasing the top 20 free and paid iPhone apps, respectively. Presuming these are in order (they're certainly not alphabetical), that puts Crash Bandicoot Nitro Kart 3D for paid apps and Facebook for free apps. Interestingly, Crash shares with Super Monkey Ball the dubious honor of being the only two apps on the list at $5.99, the highest price here. Eight of the paid apps cost $0.99 apiece, and the rest fall somewhere in between. Check out both lists after the break.