The Helmet Project
- Documents how the helmets for each team of the NFL, NCAA, NAIA, CIS, NFL Europe, Arena football, CFL, as well as defunct professional leagues, have changed over the years, as well as any interesting anecdotes about each.
- http://www.nationalchamps.net/Helmet_Project/

Professional Football Researchers Association (PFRA)
- History of professional football, including the players, teams, leagues, games and stories from the National Football League (NFL), World Football League (WFL), United States Football League (USFL) and other professional leagues.
- http://www.footballresearch.com/