The
10-10 International Net is a
group of
Amateur Radio operators who work mostly on
10 meters (
28MHz). To join, you need to collect ten 10-10 numbers and submit an
application. After that, you get your own 10-10 number.
One of the fun things to do is paperchasing. There are many small clubs that work with 10-10 and give out certificates for contacting and trading 10-10 numbers.
Visit them at http://www.ten-ten.org