DK is reporting today that not only is Brendan Donnelly is the third reliever the Pirates were negotiating with, but that he's agreed to terms with the team.
Donnelly will be 38 on the Fourth of July, but he pitched very well in 25 1/3 innings with the Marlins last year. In fact, he's always pitched well everywhere he's been, save a short, ugly stint with Cleveland in 2008. He had Tommy John surgery in 2007, which is what cut both 2007 and 2008 short, and he spent part of last year with the Astros Triple-A affiliate in Round Rock.
Donnelly said earlier this off-season that he wasn't interested in taking a minor league deal, but there's no indication either way in terms of contracts. If this is a big league deal, it'll likely be cheap and incentive-laden. In any case, he showed last year he's still capable of being a good reliever (in addition to his low ERA, he averaged nearly a strikeout an inning with a 2.78 K/BB ratio and only one homer allowed in his 25 1/3 innings) and so long as the Pirates aren't paying him excessively (which I can't imagine that they are), this is probably a nice low-risk pickup.
UPDATE: It's a one-year deal for $1.5 million with another $1.5 million available in incentives. The deal is pending a physical, so there's probably a day or two for the corresponding roster move, whatever it is, to be made.