Just had a fascinating 2-hour session on working with geocommons.com, which lets you create all kinds of amazing map/data mashups, using publicly uploaded and shared data sets and shape files. The data behind this map of Male bicycle commuters per region is very old (from the 2000 census) – would love to do the mashup again when the 2010 data comes out in March, to see how it compares.
Takes some tweaking to get the population distributions to tell the story, but here you can see how dramatically bicycle usage increases in urban centers, i.e. where bicycle commuting is feasible, then drops precipitously as you head out toward the ‘burbs.
Be sure to enabled the Legend at lower right to make sense of the shaded regions. My only complaint is that the map has to load all of its data before it can draw shaded regions for the current viewport. But otherwise, wow – this was incredibly easy to do.