Why We Reason is an excellent psychology blog that has a great deal of subject matter in common with Less Wrong. Some of the topics discussed on the blog include social psychology, judgement and decision making, neuroscience, cognitive biases, and creativity. And there's even a hint of the kind of "cognitive philosophy" practiced on Less Wrong.

The author, Sam McNerney, is blessed with the rare gift of being able to distill psychology topics for a lay audience, and his posts are very lucid.

There's also a handy archive of every post on the site.