Where as commercial radio communications are moving ever higher in frequency because of the bandwidth they need, there are in fact a number of Ham Radio enthousiasts that are doing quite the opposite.
And I'm not talking about the in some countries relatively new low frequency bands in the Mid Wave range e.g. the 500 kHz band, or even the Long wave range.
When we talk about low frequencies we talk about the VLF band, and this Very Low Frequency radio spectrum extends from 3 to 30 kHz..
I've came across this ever interesting website of Renato Romero, IK1QFK, who has an interesting website about radiowaves below 22 kHz with plenty of links on the subject.
To my surprise there are in fact quite a number of stations in this part of the spectrum. You can find a nice list of stations in this VLF band at this link: