Elias has released its NL player rankings, which are used to determine compensation picks for free agents. Of course, the team letting the player go has to offer arbitration (which is subsequently turned down) by December or the player must sign with another team by December in order to the get the compensation picks.
As best as I can tell, the only Cardinals free agents that would bring compensation are Eckstein (Type B) and Percival (Type B). Both would net the Cardinals a sandwich pick if they leave.
AL Rankings (worth considering -- along with the NL Rankings -- if the Cardinals pursue certain free agents) are here. I believe under the new rules, a Type A nets a sandwich pick for the former team plus a transfer of the first round pick of the signing team (picks 1-15 protected, and the Cardinals are at 13 -- so would give up their second round pick to sign a Type A FA) to the former team.