Across the radio spectrum, there are a whole heap of interesting frequencies where you will find activity. Over time I plan to slowly compile a list of things to listen for.
20m Band (14Mhz) 14.070 Digital Modes (Mainly PSK31) 14.076 20m JT65 Calling Freq 14.230 SSTV Calling Freq 14.236 FreeDV Calling Freq