I have helped track down a few illegal ops myself... it usually starts when a hams neighbors start experincing interference, and of course blame the ham. Once we determine it is not the amatuer operator (and only in one case out of 30 or 40 was it) we start tracking down the source of the intereference. 90% of the time it is coming from illegal CB operaters, but we have tracked it also to a recently relocted municipal base station, a state trooper who just moved in and caused his neighbors TV to cut off whenever he transmitted from his drivway, and some other interesting cuases.
If it is an illegal operation, we document it and send the data to the FCC. The FCC is much more likely to investigate and take action if you foward all the info done for them. Just a compliant of interference is unlikely to get any action, but a complaint that is accompanied by recordings of the offending station, logs of activity, and the location of the transmitter with pictures of the building many time will.
Interestingly enough, if the station is legal and conforms to good engineeriing practices, the law says that the person who owns the equipment being interefered with is responsibe for fixing or upgrading thier equipment. So if my amatuer station causes your home alarm to go off, if my station meets FCC requirments than it is up to you to fix your alarm (most hams will work with people to fix any issues, but legally they don't have to).
Tango7, if you are still having the trouble look up your local amatuer radio club and ask if they want a real-life fox hunt.... they may be willing to track down the source of the problem for you. If it is CB operaters, the FCC has extended authority to enforce laws applying to CB's over to local LE, so you may be able to get them off the air without the FCC.