The Massachussetts Referee Commitee - where you sign up for recertification and upgrade courses
Ask a referee - where Jim Allen answers your questions about things that happened in your games. Updated twice a month
MLS Week in Review - where you can see film clips of recent MLS games and hear what te referees did well or should have done better.
Soccer Spot - your local referee supply store
Official Sports - the web site of the official referee supply house of US Soccer.