Just catching up on some things I missed when I was out, but the Pirates have signed pitchers Denny Bautista, Chris Bootcheck and Juan Mateo; corner infielders Garrett Jones and Andy Phillips; and outfielder Jeff Salazar to minor league deals. Bautista and Mateo were both with the Bucs last year.
Bautista and Bootcheck will both be considered for bullpen jobs, but Mateo actually may be the one with the most promise; he just turned 26 and pitched very well for Altoona last year.
Jones once appeared to be a prospect for the Twins, but he apparently peaked at age 23 and has never posted the sort of numbers you'd hope for from a first base prospect at AAA. He'll hit some homers for Indianapolis, but he'll only be with the Pirates in case of emergency. Phillips might be on the Pirates' bench at some point--he's most famous for flopping in multiple opportunities with the Yankees, but he's always hit well in AAA and he can play third base as well as first. He can also play second in a pinch. Salazar's mostly modest numbers at AAA are even less impressive than they appear, as he posted them in good hitting environments, but he's played decently in brief major league stints for the Rockies and Diamondbacks; he isn't a prospect, but he might might be useful on the Pirates' bench.
UPDATE: Vlad has some more good information, and some projections, in the comments.