Who are the best science writers?

This is becoming a bit of a meme. It started when T. Ryan Gregory decided to post a list of good science writers in an attempt to balance the Internet's readiness to slate dodgy science writing with a shout out to the ones who do it well. Brian Switek, himself a worthy addition to Ryan's list, took up the baton and asked his readers to name good science writers. I want to do the same. This blog has always been about highlighting good science rather than crushing its darker pseudoscientific counterpart, so it seems only fitting that we should take some time out to celebrate decent writing. And there's loads of it about. So tell me - who are the best science communicators? Given the nature of this blog, please restrict your answers to people to are exceptional at explaining science to a non-specialist audience. Don't limit yourself to bloggers - let's hear it for jobbing journos, big name science writers, broadcasters, and so on. Go.