Zach Levine has a note in his blog post detailing who has signed from the 2010 draft class.
Also, second-rounder Vincent Velasquez can't sign yet because he doesn't graduate from high school until June 22. Also, 10th-rounder Evan Grills from Ontario, Canada, is still waiting to start final exams.
I wonder what happens if you draft a high school player who doesn't graduate. Do you have to graduate high school to play major-league baseball?