ARRL is the American Radio Relay League, of which I am a proud member.  They are the American organization that looks out for our rights as Amateur radio operators, and offer a plethora of services to Hams.  Their website is the best location available to find out about anything ham related and extensive.  They help you with getting licensed, and you can look up what callsigns people have, or the name the goes with a particular callsign, among  many other services they offer.  You could take days just looking  through their website!

I encourage all new hams to join!