I don't think it's a good idea to tap cars. Even if you're in the right, it makes you look like a fanatic, and won't help the cyclists that the driver will encounter in the future. Unless I actually have a collision, I just let things go now. Last week, I got right hooked, and I just got up, went to the driver's window, and, even though I was angry, just politely asked the driver to be more careful next time.