Johnny Giavotella was called up by the Royals and will be their starting second baseman. He can provide a decent average with a strong OBP and moderate power/speed. He'll mainly be useful in AL-only leagues.
Although Josh Johnson's 4.89 ERA is unlucky (.345 BABIP), it should be clear to many that he isn't the same front of the rotation starter that he once was. I think the most likely scenario for the rest of the season is an ERA around 3.75.
The Orioles traded for Scott Feldman and he's immediately worth a pickup in AL-only leagues although I wouldn't waste my waiver position on him. Here is a piece from earlier in the week covering Feldman: http://www.faketeams.com/2013/7/2/4488760/orioles-acquire-scott-feldman
It's time to pick up Alex Avila if you need a catcher. He hit well in his rehab assignment and hit a HR yesterday. Perhaps he can turn things around moving forward and has potential to hit about 8 HR with a .265+ AVG the rest of the way.
Clay Buchholz looks like he'll be ready to rock after the all-star break. Hopefully he can regain his form from earlier in the year.
Brett Lawrie will likely be able to return after the all-star break and could be a difference maker the rest of the way if he can just stay healthy.
Alexi Ogando should be return shortly after the all-star break.
Peter Bourjos will miss most of July with a fractured wrist. J.B. Schuck will get extra playing time while he's out but I don't think he's worth a pickup due to his very minimal power/speed.
Justin Maxwell should only miss a week or so with concussion-related symptoms. He can help those in need of power/speed that can afford to have a low batting average in their lineup.
Jesus Montero will begin playing in minor league games and will make his transition to 1B/DH.
Alex Rodriguez began his rehab assignment and could be activated after the all-star break. It's questionable whether he will be able to stay healthy in addition to his likely production level after his rough second half last season.