The Pirates have signed third baseman Andy Marte, pitcher Fernando Nieve, and catcher Dusty Brown to minor-league deals. Marte is the big name - he was one of the best prospects in baseball back when he was with the Braves, but he stalled badly in the Indians system and isn't a prospect anymore. He seemed to have peaked at age 21 and is now 27, and hasn't really even hit Class AAA hitters all that well since back in 2005. I assume he'll play third for Indianapolis (UPDATE: as Adam Reynolds points out in the comments, he could also play some first base, since Josh Harrison will probably be at third most of the time), but I'm sure the Pirates will treat him as an organizational player and won't let him block prospects. I'm all about signing former top prospects, but I don't think anyone actually thinks there's still real hope for this guy.
Nieve came up through the Astros system and spent the last two years with the Mets. He doesn't have much of a track record in the majors, struggles with his control, and somehow managed to allow ten homers in 42 innings in the majors last year, but he throws hard, with an average fastball velocity of over 93 MPH last year. He'll likely just provide bullpen depth at Indianapolis, but even at age 28, it's not totally ridiculous to think a pitcher with his velocity could learn something down there and end up helping in the majors.
Brown was the only one of the three I wasn't already familiar with, and that's because he's strictly minor league material - one of those AAA backup catchers who doesn't hit much, like Luke Carlin last year.