I’ve just come across the Jepson Flora Project, which
brings together all of the floristic references and data of the Jepson Herbarium. Resources of the Flora Project are directly linked the the Consortium of California Herbaria, CalPhotos, the California Native Plant Society, California Exotic Pest Plant Council, USDA-Plants database, and many other external sites. The Friends of the Jepson Herbarium help the Jepson Flora project carry out its work.
It doesn’t look particularly nice, but I do like the idea of aggregating all kinds of information about each taxon, like Helianthus californicus for instance, via the Jepson Online Interchange. From that admittedly ugly page you can dig deeper, and for example get a digest of taxonomic, distribution and phenology information based on specimens from members of the Consortium of California Herbaria. They don’t make it particularly easy for you ((You have to walk the data through the Berkeley Mapper.)) but you can, wonder of wonders, even export the location data to Google Earth, where you can mess with it as you wish.
I wonder how many other US states have something similar. And whether all their data on crop wild relatives could then automagically be aggregated up to the national level. Colin, are you there?