Well, we never thought it would happen because of its intense rivalry with Google, but Facebook is almost ready to launch an official app for Android phones. Hints are already popping up here and there, but I’ve been able to confirm it. The app could hit the Android Market (its version of the App Store) as soon as the end of this week.

Facebook’s Android app will launch with a more limited set of features than its current, and very popular, iPhone app. For instance, it won’t have an inbox, I’m told by a source who has seen it. But it will have the full Facebook stream, which is really all you need. The Facebook Android app is built around the stream and status updates. It was built with Facebook’s new Stream API. Your updates keep coming in, with a notification number telling you how many new items are available at any given time.

As recently as last October, Facebook had no interest in building an Android app. Why help its arch-rival Google? Back then, Michael wrote:

From what we hear, Facebook has dedicated exactly zero resources to creating a version of the service for Android, and has no plans to launch anything at all.

So what changed? Well, for one thing, Android is now on the verge of becoming a serious competitor to the iPhone, with nearly two dozen new phones set to launch this year. For another thing, the Android team at Google offered to help, and even loaned Facebook an Android engineer. Facebook still doesn’t have one of its own, says my source. (Facebook wouldn’t comment). Some Google engineers are already using the app like crazy.

Meanwhile, we are still waiting for the next version of Facebook’s iPhone app, which will include events, video uploading, and so much more. The current app, which many social networking junkies find indispensable, launched a year ago.