prop.kc2g.com ...provides near-realtime maps and data about ionospheric conditions, for the use of amateur radio operators.
The MUF map shows the Maximum Usable Frequency using colors and
contour lines. For example, if a given area on the map is greenish
and lies between the contours labeled "15" and "17", then the MUF
is around 16MHz in that location. The readings from each
individual station are shown as colored dots with numbers inside
them, so you can see where the information is coming from. If a
dot is faded out, then that station currently has a low
"confidence score".
Example