There's some pretty cool data hosted at the McGill Geology department, and I took a peek at the first set on Global Cropland and Pasture data from 1700 to 2007 (whoa!).
It's in NetCDF format (yeah, I hadn't heard of it either), which is pretty cool because it holds a bunch of time slices of data, so in just one file you have ALL those years from 1700 through modern-day. Plus it's a relatively small file and really easy to flip through those years in Arc. I'm still trying to figure out how to get ArcMap to play nicely with it in raster format, as the Raster Calculator seems displeased trying to operate on the data.
So here's what I came up with: a combined map of land use for crops and pastures in the year 2007. Pastures are blue and crops are green, and overlapping areas are various shades of turquoise, going all the way to dark dark green-blue. (Very pale greens and very pale blues means there's not that much of either, but there's even less of whichever color isn't showing.) Pretty intuitive with the different areas (northern parts of Africa/Canada/Russia aren't used for much of either, midwestern US is for both, and so forth).
