Much of this may seem off-topic - sorry.

HAM

Not sure where the term HAM comes from but it means Amateru radio operator. The FCC stepped in a few decades ago and decided that we couldn't just turn a radio and broadcast on whatever frequency we wanted and since then they have been making a bundle auctioning off the rights to broadcast of specific frequencies. The existing amateur radio community at the time decided it was better to allow this and pay a lisencing fee to the FCC in order to continue broadcasting on as many frequencies a possible. The lisence signifies that you know the limitations both to power and frequency that apply to amateur radio broadcast and that you are capable of operating your radio in a polite manner that doesn't make it difficult for another to communicate via the same frequency. As with all lisences it can be viewed cynically as another opportunity for the government to tax the citizens and remove their liberties - or optimistically as the valid operation of government regulating a public resource to prevent abuse of some users at the hands of others. In anycase you will need to take the course, pay the fee and have the lisence before you do much broadcasting on the amateur frequencies.

You can, of-course, get an amateur radio quite readily and go ahead and start broadcasting. It is easy to trangulate on a radio signal and there are othere HAM's out there who will resent your broadcasting without having paid the fee and they will turn you in. I think that the penalty fee is probably worse than the lisencing fee. The class is usually a 4 hour saturday affair where they will teach you how to cheat your way through the test. The questions in the test are known ahead of time and the instructors will teach you the answers to the questions - no more - no less.

Of course if you want to get truely into the spirit of the hobby you will want to take a basic electronics course, a basic radio theory course and probably a true corse on radio operations, read the ARRL Operators manual (400+ pages) and really understand the theory, operation, circuitry and regulation of amateur radios. Then take the test and you will pass with flying colors (and have a new, exciting, expensive hobby and probably a $3000 100foot or taller radio tower in your backyard within a year while you chat in morse code with new friends in Japan, South Africa, in orbit, and anywhere else that humans happen to be.) Yes you can reach that far with an amateur rig costing under $1000 - even with a home-brew rig costing less than $200 - That's where the fun really begins in this hobby.

links
HAM
FCC's Amateur radio page
Amateur Radio Relay League
FEMA on Amateur Radio
Radio Amateur Civil Emergency Service
Amateur Radio Emergency Service
SkyWarn weather spotting amateur radio operators
U.S. Army Military Affiliate Radio System
U.S. Air Force Military Affiliate Radio System
Radio Amateurs and the Boy Scouts

CB
Radio Emergency Associated Communications Team

There are a bunch of other organizations out there using various radio frequencies as emergency communications. I have only listed U.S. services and organizations that I am aware of but I am sure that if you contact your local Gov't they can guide you to the Amateur radio operators locally. You'd probably get a decent start for international organizations from the ARRL web site.