Upper Air

Balloon Lift With Lighter Than Air Gases - University of Hawaii
Ballooning and Meteorology in the Twentieth Century - U.S. Centennial of Flight Commission
Balloons Sample the Weather - The Weather Doctor's Weather Almanac
Launches of Instrumented Balloons in Storms - Thunderstorm Electrification and Lightning Experiment
NASA Balloon Program Office - Wallops Flight Facility, Virginia
Pilot Balloon Resources - Martin Brenner, California State University Long Beach
Upper Air Observations Program - National Weather Service

Airgas - US distributor of industrial, medical, and specialty gases and related equipment
Rocketman - High altitude balloon payload recovery parachutes
Simple Homemade Balloon Filling Device (PDF)