I want to recommend Child's Play. It's a blog about child development research by Melody Dye, a researcher in cognitive science at Stanford, and Jason Goldman, a graduate student in Developmental Psychology at USC. Right now they're doing a series of posts on dyscalculia (math dyslexia, more or less). They seem like they have good attitudes, know a lot, and write clearly about interesting subjects. What more could you want?
UPDATE: Jason has a related post on the origins of number representation at his other blog, the Thoughtful Animal. Jeez, there's a lot of good stuff mixed in with the crap on the internet.