In my little piece of surburbia, school buses tend to scare me the most. There are a lot of them out immediately prior to rush hour which just happens to be when I'm commuting by bike. I think that school bus drivers are so used to everyone else yielding to them (which is a good thing since my kids are passengers), that they simply ignore cyclists. I've been cut off, squeezed onto the shoulder, and forced to ride behind these fume-belching monsters far too often. Rant over.

(P.S. I own two bimmers and take offense at the anti-Munchen motors attitude ;-))