Here's a link to 3 propagation maps.
The first one is the "D-RAP map." This map shows the maximum usable frequency due to D layer attenuation. This one applies for daytime operation.
The second map is the foF2 map. There are sensors that send up a chirp from the broadcast band to about 13 MHz - straight up. These sensors look at the return signal and plot a map based NVIS (Near Vertical Incident Signal). This is the mode most of use particularly on 160 , 80 meter operation
The third map is the DX map and as the title indicates shows long haul comm... Check them out at:
http://www.w1vtp.com/propagation_maps.htm
