Ontario's Air Monitoring Stations
This Google Map from the Government of Ontario, Canada shows the ozone concentration measurements from Ontario's air monitoring stations.
The map automatically shows the latest measurements but it is also possible to view the data for any hour in the last four years. A really nice feature of the map, and one I haven't seen on a Google Map mashup before, is the use of map insets. The map insets show in close up selected areas on the map.
If you click on any of the mapped air monitoring stations you will be taken to the station's home page.
Via: Street View Funny