For Joe Martinez. Martinez (stats) is a 27-year-old starting pitcher who looks capable of pitching in the big leagues right now, albeit not particularly well. He's a groundball guy, which is good, because that should stop him from coming up like Daniel McCutchen did and getting rocked. He doesn't throw hard, but other than that, nothing about his game really stands out as a weakness - his strikeout rate isn't high, but it's reasonable; he doesn't allow too many walks; and he keeps homers off the board. Here's a good profile of Martinez. Overall, again, I'd prefer the Pirates tried to acquire prospects here, but Martinez is a very good value for a pretty generic lefty reliever.
UPDATE: The Pirates also get outfielder John Bowker, according to Dejan Kovacevic. Bowker is 27 and has struggled in the majors, but has posted huge numbers in Class AAA. It's not clear how the Pirates can use him, though.