This is probably already being done, but...
What do you think about creating a database that contained license number, state, car type, color, make, details of the near miss (or hit) and perhaps other information of the cars (and owners) that are creating problems for bicyclists.
I would envision an online entry form where you can enter information about the event. Possibly an additional form so that the person being reported on could respond (unlikely!).
It would be available online for anyone to search by state, license number, car type/color, etc. to determine if a person (car) has a history of trying to run down or harrass a bicycle rider. Over a period of time, as the amount of data increases, I can see that it could be useful for law enforcement and/or court actions against some idiot that is a repeat offender.
If it is being done, can someone post a url to the site. If it is not being done - do you think the idea has any merit? What kind of information would you think should be kept on the offending motorist? Other suggestions?