As if we don't spend enough time on Facebook, more than 9 million apps and websites are integrated with Facebook to suck you farther into the social network. While winnowing that vast number down to a handful of the best ones is no small feat, here's a good start.
These Facebook apps are favorites of PCWorld writers and editors, see incredible traction with users according to AppData (the Facebook traffic monitoring site), or are notably useful or fun and yet probably not on your radar. All are available in free versions, though you get more features with some if you pay. Enjoy.