According to an article posted by Steve O’Hear at ZDNet. here is a list of the top 5 Facebook Applications. (Descriptions provide by ZDNET)

1. iLike integrates the music social network and recommendation service into your profile. Adding music-based social networking to Facebook makes perfect sense, and is something they could have easily done themselves. That’s what makes the company’s Platform strategy so intriguing. Mike Arrington (over at TechCrunch) also notes the omission of Last.fm which is arguably the best-of-breed of music-based social networks.

2. Horoscopes (by RockYou!) adds twice-weeky horoscope readings to your profile.

3. The Compass (by the Washington Post) involves taking a survey that determines your political compass. The results are then displayed on your profile. It’s a fun idea, but hardly qualifies as an ‘application’.

4. Games adds multiplayer web-based games to Facebook: “Play games and meet new people in your networks! Add the Games application to get access to a constantly changing selection of fun multi-player games, all right in your browser.” Pretty obvious but neat idea that has the potential to take traffic away from dedicated web-based gaming social networks. If the games are any good that is.

5. Picnik adds basic photo editing functionality to Facebook. Considering that the social network has been reported as the largest photo-sharing site on the web, giving users the ability to re-size, crop, and enhance their photos without leaving the site is a smart move. Although again, it seems like the kind of thing Facebook should have done themselves.

Its seems like more and more people are catching on to the new Facebook applications and Facebook Platform, it will be interesting to see what new application will come of it.

Facebook Platform is here. Now you can choose what applications you want.

Browse the applications in this directory and find what will be the most useful or relevant for you. Once you add applications, you can edit settings and privacy from the My Applications page.

The next evolution of Facebook Platform was unveiled this week at the Facebook f8 developer event at the San Francisco Design Center.

With this evolution of Facebook Platform you can now build the next generation of applications with deep integration into Facebook, mass distribution through the social graph, and a new business opportunity.
Deep Integration

You can now build applications that have the same access to integration into the social graph as Facebook applications, such as photos, notes, and events. Over ten integration points are now available, including:

Canvas
Profile Box
Profile Action
News Feed
Mini-Feed
Left Navigation
Requests
Notifications
Emails
Messages
Share

You can access these integration points using the all-new Facebook Markup Language.
Mass Distribution

The power of mass distribution is now in your hands. You can gain distribution for your applications through the social graph like never before. Applications can be virally engineered to reach millions of Facebook users quickly and efficiently through the profile, news feed, and mini-feed.
New Opportunity

With access to deep integration into the site, and mass distribution through the social graph comes a new opportunity for you to build a business with your application. You are free to monetize your canvas pages through advertising or other transactions that you control. Profile boxes must remain free of advertising.

Learn more. Watch the Inside Platform Video.

Source – Facebook.com