Placebase's Pushpin API provides a format they call "GeoJSON", which should be good except that it has the wrong coordinate order. Easting and northing are swapped and the data is therefore tilted over, which is bad. See for example
The sooner this gets fixed, the better for all of us. Anybody got a line to Placebase?
Update (2008-05-24): The Pushpin response is fixed. I'm excited to see GeoJSON catching on like this.