Streetsblog had a post on seeclickfix, a new web-based infrastructure problem reporting system. In New Haven it brought attention to a dangerous railroad grade crossing that caused several bike crashes. A few DC reports have been opened - including requests to enforce the Downtown bike/bus lanes and to smooth the Georgetown Branch Trail. For many reports I'd suggest going to DDOT directly, but for enforcement issues it could be useful to use something like this - if for no other reason than to vent.
Streetsblog also mentioned a new iPhone app for reporting such things in Boston.
It's only a matter of time before we have such an item here.