"To promote and advance the art, science and enjoyment of Amateur Radio."
Founded in 1914 by Hiram Percy Maxim, ARRL (American Radio Relay League) is the national association for Amateur Radio in the US. Today, with more than 161,000 members, ARRL is the largest organization of radio amateurs in the world. ARRL's mission is based on five pillars: Public Service, Advocacy, Education, Technology, and Membership.
The Federal Communications Commission's Wireless Services - Amateur Radio related site that offers a new ULS (Universal Licensing System) for all amateurs and prospective amateur operators. Also the current Title 47, part 97 rules are located here
QRZ.com is a wonderful resource for amateurs. Asside from hosting a license holder database that is updated daily from the FCC's ULS database, there are many articles, forums and things of general interest to radio amateurs.
And naturally, you may rely on the membership for information and guidance in the areas of amateur radio, and topics of all types that relate to what we employ in our day to day lives as radio amateurs.