Thanks to Nick Erpelding (a friend of mine who's a traffic engineer at Westwood Professional Services) for sending me this photo of the "Traffic Calming Turtle." Nick tells me they're on sale at Costco (I'm working on a study for Costco so I feel like I should pass on this promotion). It's just in time for the spring speeding problem on your street. I have a neighbor who puts one of these out in my alley.
I prefer to put out a tricycle, wagon or ball when my kids are out playing. I think a bunch of toys by the side of the road or the alley does a better job of slowing down cars than any kind of "official" sign.
Nick tells me he was bummed out when the city filled in the potholes in front of his house. They were great for traffic calming. He's gone ahead and planted some trees in his front yard to eventually make the road feel narrower.