Here's another interesting site: the Encyclopedia of Earth. A combination of on-line reference, science-education and activist portal, it's edited by some people at Boston University and boasts an impressive-looking community of scholars and writers.
I found the EoE while searching for ways to think about bioregionalism in Ohio. There's not much out there. Like some other powerfully suggestive concepts, it seems best adapted to particular regions--like the Pacific Northwest--where the distinction between different regions is sharply marked: geography itself there seems to call forth conceptual work. Elsewhere, the gradations are subtle and somewhat arbitrary: what should count as a bioregional marker? An encyclopedic mind--one that wants to have everything covered--would look for a uniform labeling system, by disembedding our knowledge of bioregions from our lived awareness and embodied practices. To be effective, I think, there must be something directly compelling about our vision of the earth: it may be refined by experience, but it has to be grounded.