A few of the recent pieces I've liked:
Ed Yong at Not Exactly Rocket Science: The disease trackers
Maryn McKenna at Superbug: How Much Is a Drug-Resistance Death Worth? Less Than $600
Michele Norris at NPR: Why Black Women, Infants Lag in Birth Outcomes
Fred Pearce at Yale Environment 360: Phosphate: A Critical Resource Misused and Now Running Low
Gina Kolata in the New York Times: First Study of Its Kind Shows Benefits of Providing Medical Insurance to Poor
And for what will surely be a source of many excellent blog posts in the future, check out the new Scientific American blog network.