It's at 10:00 AM. Here's Vlad's awesome preview.
Update (by Vlad): There's a live audio stream of the draft available here.
Update (by Charlie): The Pirates have selected Gustavo Nunez from the Tigers. He played at Class A+ and Class AA last year, and didn't hit at all at Class AA (.215/.252/.289), so this is a weird one. He's a shortstop. He did hit pretty well at Class A+ (.304/.368/.431), but he was 23, which isn't young, and he has a long history of not really hitting much. Here's his profile. Even if he's amazing defensively (Baseball America says he is a "highly skilled defender" with a "highly questionable bat"), I don't see how the Pirates can possibly carry him on their roster all year, so I'm not really sure what they're thinking here. Then again, I didn't understand why they carried Pedro Ciriaco for months at a time, either.
The Diamondbacks have picked Brett Lorin. Diego Moreno was not selected.
In the minor-league portion, the Pirates have picked pitcher Aaron Poreda from the Padres. San Diego acquired Poreda from the White Sox in the Jake Peavy deal, but he was extremely wild for them. He's 25 and will continue to be a project, if the Pirates even think of him as a prospect at all.
The Pirates also picked Francisco Diaz, a young but light-hitting catcher from the Phillies.
The Bucs have also selected catcher Charles Cutler from the Cardinals. He was 24 in 2011 and hit very well at Class AA. He also goes by "Charlie," which is always cool with me. I can't find anyone on the internet who thinks he's much of a prospect, despite the good hitting numbers.
Update (By Vlad): Coming out of high school, Cutler ranked as one of the better catching prospects in the country - BA had him listed as their #169 overall prospect (and #31 in California) for the 2005 draft class. He struggled a bit with the bat in college, though, and his stock dropped. He's apparently Jewish, and interested in playing for Israel in the WBC in 2013, which is kind of neat. He also had some knee problems last year, which could be a significant concern for a catcher.