While you're probably already dallying with social networking sites (if not full-on obsessed), you might not realize they've become powerful tools for making professional connections. In fact, if you're not participating in these sites for business purposes, you're at a disadvantage. "When they're used effectively, social networks take the concept 'It's who you know' to a whole new level of exposure you can't get any other way," says Jeff Zbar, the creator of chiefhomeofficer.com Get up to speed with these books: Twitter Tips, Tricks and Tweets, Facebook Me! and Me 2.0 Build a Powerful Brand to Achieve Career Success.