When people tailgate me, I tap my brakes (just enough to make the lights go on) a few times, and look for a place to pull right to let them pass. If they don't take the brake light hint, and I can't pull right at the moment, I leave more space in front of me to compensate for their stopping distance as well as my own, until I can get out of their way. I don't let them pass in order to be accommodating though, I do it because being near someone who drives that way is less safe.