After reading the posts here about USGS data no longer free, I went to look for my self, and I found this site. Not sure if this data is still in the format Terrascene needs, but the USGS still provides data for free. It appears though they are using a new interface (Graphical) to get it, here is the link.http://seamless.usgs.gov/website/Seamless/

Terrascene would need to be able to access the information the graphical interface accesses. This might be a good time though to look into creating an updated program that would be able to pull from the satellite imagery and produce tiles with those images. That would be even faster than compiling roads, rivers, landclass, etc. If you could pull up accurate shorelines, hi res elevation data then the satellite imagery imagine the results. Yeah, I know what about night images and what about the images that have clouds in them, but just thinkin aloud.