There are several weather satellites which are in a polar orbit. That means they are going from pole to pole and the earth is moving below them and this way they can visit the complete surface of the earth within a few days. And the best thing is they are sending unencrypted data back to earth in form of pictures from the surface.
The NOAA satellites are the most famous ones, but there are others like MetOp and FengYun. The NOAA satellites are using the APT (Automatic Picture Transmission) in the 2m band and HRPT (High Resolution Picture Transmission) at 1,7GHz. The MetOP and FengYun satellites use only HRPT at 1.7GHz. Check out the Frequencies page for a comprehensive list of the used frequencies.
To receive the data send by the satellites you need only a RTL-SDR stick and a helix antenna. The HRPT can be a bit difficult as 1.7GHz is near the upper limit of the RTL-SDR stick, but it should work. The helix antenna is easy to build.
http://jcoppens.com/ant/qfh/calc.de.php – Rechner für QFH Antennen
https://www.eumetsat.int/media/43321 – HRPT specification