The Cardinals have acquired John Lackey, which is annoying. Lackey was a quiet presence on this market, but he's a very effective starter, posting 2.5 WAR already this year and 3.1 last year. Right now, the Cardinals appear to be the team seizing the day in the NL Central, and with Jon Lester off the market, it won't be easy for the Pirates to counter with a move to offset the progress the Cardinals have made.
The Cards also, of course, recently acquired Justin Masterson.
UPDATE: The Cardinals gave up Allen Craig and Joe Kelly, which will dramatically change their outlook going forward. Craig was signed to a long-term deal. It should presumably be a bit easier for them to find playing time for Oscar Taveras now. This is a nifty buy-low move for the Red Sox as well. Suddenly their outfield, which had been a big disappointment for them this season, looks a lot more interesting.
UPDATE 2: By the way, I think this is fine for the Red Sox, but it's not clear to me that it's a steal for them. Craig has been horrible this year, and Kelly hasn't pitched well either. I expect Craig will bounce back to a degree -- his BABIP this year is very low. But if he doesn't, his contract will be a minor annoyance.