Landsat Imagery Source

Another source for Landsat imagery (this one from U. of Maryland Global Land Cover Facility).

US Aerial Photography Program

See this link from GIS Weekly on the Digital Orthophoto Program. Includes information on nation-wide DOQQ availability.

Data and more data

Perhaps you already know about this site, but ... just in case: http://glcf.umiacs.umd.edu/index.shtml . They have 13 Terabytes of available data, so it’s likely you can find something interesting. Landsat, Modis and Aster imagery and products, with different search methods.

That’s one big marble!

NASA released a new version of their "Blue Marble" whole Earth image. Blue Marble is their name for the stitched, cloud-free imagery they've gleaned from MODIS. They've done this before, but the new version (called Blue Earth: Next Generation -- original, I know) has better resolution (0.5 km vs 1 km) and more temporal data (12 months instead of 4 3-month intervals). The file sizes are huge, but they look great. Take a look!