Facebook tonight unveiled its mobile App Center as it amps up its efforts to improve its mobile business.

The new app center, the company’s first big announcement since its IPO, went live tonight with more than 600 apps, including Nike+ GPS, Ubisoft Ghost Recon Commander, Stitcher Radio, Draw Something, and Pinterest.

The App Center is designed to offer an experience personalized for each user, with app recommendations based on the apps they and their friends use. So if you’re a person who likes word games — something Facebook would know from your Facebook behavior — the App Center will surface those sorts of apps for you. Then, when you select an app you like, you’ll be sent to the Apple’s App Store or Google’s, depending on your device.

Even so, most Facebook users will have to wait before they can check out the App Center. Tonight’s rollout — full of big stats and optimism — will only go live for between 6 percent and 8 percent of Facebook’s U.S. users, said Matt Wyndowe, the company’s product manager for games and apps. The company it will roll out to all U.S. users in the coming weeks. Eventually, said Wyndowe, there will be different App Centers customized for different parts of the word.

The App Center is available on mobile via the Facebook apps for iOS and Android, and by accessing Facebook.com on mobile. A huge amount of Facebook’s mobile traffic goes through the mobile Web, not via apps

The announcement comes a month after Facebook first said it was launching an App Center, which it billed mainly as a way to help users discover the best social apps and to drum up interest from developers.

Facebook is under enormous pressure to figure out ways to make money from mobile. And in the run up to the IPO, Zuckerberg told investors that mobile was his key priority for 2012.

Of course, it’s also about how Facebook gathers data from its users. In that way, the App Center should help a ton as more and more people use apps that are integrated with Facebook.

The company has recently been making others changes to its mobile products as well. Just yesterday it rolled out a “low-friction” mobile payment system to make it easier to make payments for virtual or digital goods via its app. And last month it redesigned its mobile interface to display larger photos.

Facebook had 488 million monthly average unique users of its mobile products in March — more than half of its 901 million users in all — and is only just starting to experiment with ways to make money from mobile. One problem is that it simply can’t show as many ads on a mobile device since the screens are smaller.

Facebook’s mobile challenge — a challenge shared by most all Web companies — has contributed to the wave pessimism about Facebook’s stock. Shares of Facebook closed today at $26.31, more than 30 percent down from their offering price of $38 a share.