Direction Finding
From BMG Engineering, Inc.

The DX Zone
A search engine and general guide including amateur radio and shortwave.

Exam Session Search Engine
From the ARRL.

FCC Database
FCC database of callsigns, frequencies, etc.

FCC Index of Forms

FCC Rules Part 97
From Gainesville Amateur Radio Society.

Global Positioning System Overview
From the Department of Geography, University of Texas at Austin.

Grid Square Converter
From AMSAT. A form that allows you to enter either a grid square locator or the latitude and longitude of a location.

Ham-Links.org
A very comprehensive and well categorized list of amateur radio links.

HamRad
The Amateur Radio Operators guide to manufacturers, dealers, and organizations as well as the home of the HamRad Trader.

K8DTI's Frequency Page
Amateur, police, fire, railroads, etc. are all covered (or soon to be) here.

Keplerian Elements
Weekly Keplerian elements from AMSAT.

Keplerian Elements Tutorial
Based on the documentation provided with InstantTrack.

National Hamfest and Convention Calendar
From the ARRL.

The Packet Radio Homepage
From TAPR. Features information and links related to all forms of amateur digital communications, including APRS.

QRZ Online Callbook Search
Official home of The QRZ Ham Radio CDROM. Online callbook search and more.

Radio Modifications FTP Archive

Radio Shack Scanner Mods & Info

Radio-TNC Wiring Diagrams
Alphabetical list of Radio-TNC manufacturers and their wiring diagrams.

RF Safety Calculator
From the University of Texas Amateur Radio Club

Shuttle Amateur Radio Experiment (SAREX)
A long-running program to use amateur radio equipment on board NASA's Space Shuttle.

The Six Meter Amateur Radio Band FAQ
Designed to help encourage hams to use and enjoy the 6 meter band.

Space Environment Center - Radio Users' Page
Providing radio operators with current data on the state of the ionosphere.

Spread Spectrum Communications Page
Providing the latest information on experimentation with Amateur Radio Spread Spectrum Communications. From TAPR.

U.S. Naval Observatory Master Clock
Realtime web clocks.

The WWW Virtual Library's Amateur Radio Page
The amateur radio category from a directory started by Tim Berners-Lee (creator of the web).