Just in case some people might not know where to find him: http://slatestarcodex.com/ (Remember to give parent comment your upvotes, not me, if you want to vote for him.)
Currently Scott Alexander has 41 votes and everyone else has a total of 28. That's pretty impressive.
FWIW, I unsubbed from MR shortly after subscribing. It kind of felt like reading through someone else's RSS feed, with small amounts of commentary which often assumed more economic literacy than I actually have.
Also, Kevin Simler's Melting Asphalt is great and has lots of insightful essays about things. Warning: Still doesn't have archives, you're going to need to go through the meta posts to read old things.
I like Eneasz Brodski's Death is Bad. Not as moralizing as the title sounds, has lots of fun book reviews.
Andrew Gelman wrote Less Wrong's favorite textbook on advanced Bayesian statistics. His blog is here. Some good stuff like a recent post on why the hot hand actually exists which I still don't completely understand.
I wonder if anyone has made any effort to systematically catalogue academics who blog?
I want to check out more rationalist bloggers.
Please list no more than one per answer. That way I can see from the upvotes/downvotes which ones are the most popular (and hopefully which ones are most worth checking out).
I know that popularity isn't a perfect signal, but hopefully it is a better signal here than on the rest of the Internet.