A presentation on Amateur Radio given at the DEF CON Hackers Convention is now available on YouTube.
The YouTube description says:
Speaker: JonM, Security Consultant & Amateur Radio Operator
Think amateur radio is all about dorks with walkie talkies? Think again. Amateur radio presents one of the last bastions for open radio experimentation. This talk will provide a brief introduction to amateur radio, explain the advantages of licensed spectrum for experimentation, and describe how to get involved in the leading edge of radio hacking.