I can't keep up with everything Chillingo is putting out on the App Store lately -- they're really kicking out the jams over there.

Sketch Nation Studio started out as Sketch Nation Shooter last year, a "game" on the App Store that actually let you make your own shooter game by using scanned-in pictures and a few scripted sets of rules. As creator Nitzan Wilnai told me at GDC earlier this year, he heard from a lot of users that they wanted to make games other than just shooters with the engine.

Last year, patent holder Lodsys filed lawsuits against iOS developers including James Thomson, Patrick McCarron, IconFactory, Combay, Rovio and more.

Starting today, Amazon will open up its Android Appstore to in-app purchases, according to a report in AllThingsD . Its model will follow that of Apple and iOS, with Amazon taking a 30 percent cut of each purchase.

Blogger Erica Ogg over at GigaOM's The Apple Blog brought up an interesting point in a post today, wondering aloud if creativity tools will be the next big wave of iOS apps . There have always been creativity tools, like painting and drawing apps, in the App Store, but Ogg based her comment on two beautiful and well-designed apps that appeared last week and have caught a lot of attention from buyers.

We meet again, Sunday.

Imangi Studios' Keith Shepherd and Natalia Luckyanova have been making solid games on iOS for years now, from their original hit Harbor Master and their charming dual-stick shooter Max Adventure. But it wasn't until Temple Run this past year (which I first saw in an off-the-record prototype form at GDC last year) that Imangi really hit it big

Sometime this evening, some lucky person downloaded the 25 billionth app from the App Store. The graphic you see above showed up between midnight and 1 AM ET, although I wasn't able to capture the exact time

Do you like reading articles on the web, but hate all of the cruft that ends up making posts hard to read?

Update : Some of the Tamsong apps have already begun disappearing from the store. Near-clone apps in the iOS App Store ? It's not a new phenomenon, by any means; last week, developer Anton Sinelnikov had the bulk of his app library yanked from the store for plagiarism