PC World — Apple passed another impressive milestone Wednesday, announcing that 100,000 apps are now available for download for iPhone and iPod Touch owners. Not too shabby, Apple, considering your App Store launched in 2008 with only 500 applications available.

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It seems like every month or so, Apple's celebrating another milestone for the iPhone's App Store. The folks in Cupertino say those 100,000-plus apps cover categories from games to productivity tools to the inexplicable.

Here's a look back at some other apps that have shaped the iPhone App Store since it opened in July 2008:

First Apps: The App Store opened with 500 apps, including mobile versions of MySpace and Facebook, an eBay app for tracking auctions and an iPhone version of the popular console game Super Monkey Ball.

Billionth Downloaded App: Bump lets you exchange contact information with another iPhone user by bumping hands together while holding a phone in each. Apple hit this milestone last April.

First App Store Controversy: I Am Rich, an app that sold for $1000, was pulled from the App Store after a few days of "should or shouldn't it be allowed" arguments in the blogosphere. It's estimated that eight people downloaded the app during its brief lifespan.

First Explicit App: Hottest Girls, as the name suggests, is a photo gallery of over 2,000 nude, topless, or scantily clad attractive women, and it was the first app of its kind that Apple actually approved. With the iPhone's addition of parental controls in OS 3.0, Apple's paranoia about explicit material seemed to fade, though the app was later removed for mysterious reasons.

Most Controversial App (Non-Existent): Google Voice takes the prize for drawing the attention of the Federal Communications Commission after being rejected -- or merely not approved yet, as Apple put it -- from the App Store.

Most Controversial App (Existent): Baby Shaker, an app that lets you shake the iPhone to silence a crying cartoon baby, didn't last for more than a week in the App Store. But it raised questions of whether Apple should play the role of tastemaker when policing the store.

Most Popular App (Free): Facebook, according to Apple. No surprise there.

Most Popular App (Paid): Crash Bandicoot Nitro Kart 3D , according to Apple as of April. However, a report from comscore around the same time gave the crown to Tap Tap Revenge.