www.FontsInUse.com is a helpful archive of typography at work in the real world, indexed by typeface, format (media), and industry.
You can contribute your font sightings, or just browse the many examples.
Jay Nelson is the editorial director of PlanetQuark.com, and the editor and publisher of Design Tools Monthly. He’s also the author of the QuarkXPress 8 and QuarkXPress 7 training titles at Lynda.com, as well as the training videos Quark includes in the box with QuarkXPress 7 . In addition, Jay writes regularly for Macworld and Photoshop User magazines and speaks at industry events.