In wider lanes, I invite them to hold back a second or two until I find a safe way to make room for them to pass. Again I do this by riding to the left some, and often by holding them back with either a look or by holding my hand out. If there is no oncoming traffic, they will go into the next lane to pass me, just like they would for a slower car. Sometimes I even point at the reason I'm holding them up, which is usually either debris, bad pavement or a parked car to my right.
Sometimes the timid cager does not want to pass me, usually on a narrow street. If I want them to pass me quick because I see an obstruction ahead, I will actually wave them past me with my left hand. They often wave to thank me as they ride by. I think a lot of cagers around here don't know how to handle cyclists, so they are relieved when I tell them what to do.
Since the cager and I both want to avoid messy accidents and/or fistfights, we have little trouble coming to an accomodation. This probably takes a half second or less to arrange, and it almost always goes smoothly for both of us.
Usually if I get buzzed it's my own damn fault because I fail to communicate clearly and/or I'm riding sloppy. Usually I end up yelling at them anyway, but that isn't very fair if me! A couple times I have been buzzed maliciously. One time was kind of funny. I was held up at a train crossing for more than 20 minutes. After the train passed, I rode ahead in the narrow lane. The car behind me couldn't pass because of all the traffic bottled up by the train. He started honking and yelling "Sidewalk!" I thought it was hilarious that a train held him up for 20 minutes and he got mad at me for holding him up 5 more seconds!