I want to test a program for image classification that uses GeoTiff data with a separate file for each band. So I'm looking for some sample satellite data, preferably of Landsat 7, that doesn't need any further correction or pre-processing (I'm not familiar with these things and just want to do a brief testing) and can be used as is. It should be in separate GeoTiff files for each band, or there should be a way to separate them.
I already searched a lot in the web and found services like GloVis, LandsatLook Viewer or USGS Earth Explorer, but I simply don't know how to use this data, it seems to require pre-processing, which I have neither the skills for nor do I have the software for that.