Kamtronics KAM - $50
This is a basic mid 1980s digital interface. AFAIK it does packet, RTTY, FSK and AMTOR, which means it would be useful for 2m and HF things like APRS and maybe Winmail, etc.
"Why does the U.S. care which flag will be hoisted on a small piece of land thousands of miles away?" -- Ron Paul