Tyler Cowen, Scott Sumner, Reihan Salam, Will Wilkinson, Conor Friesendorf.
Picking just one conservative I'd choose Cowen without blinking because he's a volume blogger with a wide net so you'll often get the best of right leaning commentary on the subjects he's interested in.
David (son of Milton) Friedman: http://daviddfriedman.blogspot.com/