Nicholas Felton's 2009 annual report has already been widely linked. I pass it along, though, with my recommendation that it's the best of his four reports. He relinquished his usual role as data collector to the friends and acquaintances he met in 2009, asking them to respond to the same web survey and answer questions about Felton's mood, location, activity, and conversation.
Felton's technical feat here is astonishing. It's challenging enough to track a data set in a spreadsheet of your creation, organized according to your own tastes. This year, Felton had to organize and visualize data no matter how his friends decided to submit it. And in spite of that loose chaos he has designed some exceptionally lucid visualizations while also experimenting a bit with form. (He used topographical maps to represent New York instead of his usual cluster plots.) I couldn't quickly decipher his cover-page infographic but realized eventually how he was graphing the duration of his relationships across time and found the whole thing vivid and melancholy.
Felton stocks the sidebars of every page with his collaborators' exact reports ("I think it's funny that Nick carries a backpack."), which is an affectionate design choice. If his previous work could be described as a staggering act of introspection, this is their equal in extrospection, a study of friends and relationships. I suspect, in ten years, this will be the one he returns to first, and most often.
BTW: See this interview with Nicholas Felton.