With the November elections just 2 1/2 months away, I think it is very unlikely that between now and then we're going to see the slew of indictments in the various federal corruption investigations that many people, myself included, had been anticipating. It is not unheard of for public integrity investigations to yield indictments immediately before elections, but they are rare.
I think it's still possible that Rep. Bob Ney (R-OH) and William Jefferson (D-LA) could be indicted at any time. (Were it not for the legal dispute over the FBI search of Jefferson's congressional office, it's likely Jefferson would already be under indictment.) In both those cases, the guilty pleas of those close to the congressmen have made it publicly quite clear that the feds are closing in on the congressmen, and for that reason indictments of them now present less of an appearance of manipulating the election (especially since Ney has bowed out of his re-election bid).
For all the ink spilled on Jack Abramoff, the K Street project, earmarks, and other misdeeds and malfeasance, Duke Cunningham is the only elected official to have been charged thus far (Tom Delay's indictment was in Texas state court). That's not to minimize the political effects of the federal investigations. Ney abandoned his re-election effort because of them; and the Texas indictment alone would probably not have been enough to dissuade Delay from seeking re-election.
Of course it has creeped into my mind from time to time whether DOJ under Alberto Gonzales will be impartial in these various investigations of mostly Republicans. If indictments were delayed until after the November elections, the Bush Administration would be able to avoid most of the political reprecussions. So there is a conflict of interest there. But all in all, I have a fairly high degree of confidence that career prosecutors would protest loudly if they felt their cases were being undermined for political reasons. So far there are few, if any, indications that this is happening. (If you have reason to know otherwise, we're all ears; see email address above; anonymity will be protected.)