Then there are the ones who get on the expressway and sit in the passing lane alongside a truck going about the speed limit and take about 5 miles to pass the truck.
And then there's the opposite problem, which isn't an annoyance so much as a curiosity - the drivers who continually pass you, then fall behind you, then pass you again, etc. This past weekend on the freeway I was cruising in the right lane and in the span of ten miles one car passed me and fell back behind me a half-dozen times. And I had the cruise control set the whole time!