And here's another: Virginia Postrel, whose weblog is the Dynamist Blog. She's a former editor of Reason magazine, but eschews some of the wild-eyed observations that they succumb to. I've found her uniformly thoughtful and insightful, on politics, economics, and culture.
Her latest book, The Substance of Style, will definitely be on my Christmas list (if I don't just give in and get it myself first).