It seems as though Derrick Goold has some knowledge:
Houston Astros ace Roy Oswalt has told the team that if they intend to trade him his "first choice" is the St. Louis Cardinals, a league executive with knowledge of the Astros' discussions with interested teams told The Post-Dispatch...
...Without mentioning Oswalt by name, a Cardinals team official said this morning that he viewed adding an unnamed "premium player" as "a longshot." At least one team other than the Cardinals has been told the Cardinals are on top of Oswalt's preferred destinations.