Last summer I not-entirely-flippantly suggested that we skip impeaching Bush and instead impeach Cheney (link) (my friend Fensterwald gave me its blessing).
I still think I'm right on not impeaching the President. I don't want impeachment to become a habit. Besides, I think there are a lot of better things for Congress to do with its time.
I'm here now listening to John Dean on Keith Olbermann suggesting that Congress move down the impeachment food chain --impeaching, e.g., cabinet officers. Evidently it is not without precedent: David Cannadine, in his magisterial new biography of Andrew Mellon (link), points out that Mellon resigned as secretary of treasury under the threat of impeachment.
Of course, there isn't the remotest chance of getting a convinction out of the Senate, but it might be a useful way to frame up some of the investigative issues.