Jon Heyman ran down a list of early trade market candidates (position players only), and there are a few Astros on there:
At #4, Michael Bourn:
A tremendous defensive centerfielder with as much speed as anyone in the game (he leads the NL with 29 stolen bases), it's something of a surprise the Astros are listening at all. But word is, they are. Their one concern, apparently, is trouble with lefthanded pitching (his OPS vs. lefties is only .544 this year compared to .737 overall). The Braves could use speed in the outfield, though Jordan Schafer has looked a bit better in recent weeks.
At #9, Hunter Pence:
The sense is Houston wants to hold onto him even if it isn't thrilled Pence beat them in arbitration for $6.9 million this winter. Pence is not only having a big year (.321, 51 RBIs) but is seen as someone who provides a great example of how to play the game for a team in transition.
At #10, Jeff Keppinger:
The versatile player has hovered around .300 (he's at .302 now) and could be a useful man for a contender.
I understand why the Astros are listening on Michael Bourn - because Bourn switched his representation to Scott Boras. Or because Jason Bourgeois is only a year older, and is kind of the same player. With perhaps a better bat. I understand holding on to Pence for Heyman's expressed reasons, but for the life of me can't figure out why they're shopping Keppinger. He's the only 2B that can hit, unless clearing out Keppinger creates room for Jose Altuve in 2012.