The iLike service opens up to a public beta today, and you can check it out here. Although iLike is part of the San Francisco-based GarageBand, many of its developers work in the company's nondescript Capitol Hill office. Nearly everyone in that office has spent time at Microsoft, including Hadi Partovi, the former MSN portal boss who played a key role in the early days of Microsoft's Live.com strategy.

iLike hooks nicely into Apple's iTunes player and works with the massive list of songs you've listened to since you installed iTunes (yes, that list is out there). Plugging that list into its recommendation engine, it can suggest songs to you. Once you add friends, social networking style, to iLike, it tells you what your friends are listening to. It sends you to the iTunes music store or Amazon.com if you want to buy a song, and gets paid by Apple for doing so.

The service has a cute "are we compatible" test that looks at how well your music fits with someone else's, and that dating-oriented feature is sure to be a driver to the site.

How did a bunch of Microsoft guys end up working on an Apple feature? It's purely business, said Ali Partovi, Hadi's twin brother and the chief of GarageBand. Apple's iTunes dominates the digital media player market, so much so that people who don't even have iPods use it. If any other player came in a close second, iLike would have developed for it as well. But the team plans to have a Windows Media Player version in the future.

Here's GigaOM's review.