The Moose suggests that the Democrats follow a British model.
With Republicans controlling both the executive and legislative branches, oversight is virtually nonexistent. Don't expect most Republican Chairman to seriously pursue any monitoring of the Bushies over the next four years. And as we have learned in scandals ranging from Abu Graihb to Armstrong Williams, the Administration probably has much to hide.
That is why Democrats should perhaps follow the British model and assign various members of the appropriate committees to serve as de-facto Shadow Secretaries of the Executive Branch. These tasks would primarily, but not exclusively, be assumed by the ranking members of the committees. Sometimes non elected officials might fit the bill. For instance, there is already an outside de-facto Commissioner of Social Security - the incomparable and indefatigable, Josh Marshall.
While the Shadow Secretaries would not have subpoena power, they could hold investigative hearings with other Democratic members. These types of hearings are already held on a de facto basis, but it could be more formalized. The press could be a useful asset in both shining a spotlight on the agencies and echoing the message.
Democrats must be creative in the coming years. They are confronted with a cunning adversary with unlimited resources. Time for outside the box thinking.