123Quiz.net: Organises open quiz events, lists quiz leagues and pub quizzes.
British Othello Federation: Independent body organising tournaments around the country and promoting the game of Othello.
BuzzerQuiz: Open and student quiz competitions in the UK, including the Championship Series and the British Student Quiz Championships. Matches closely resemble University Challenge / College Bowl.
Mind Sports Olympiad: Organisation based in London that provides an event for lovers of games and mind sports to battle for prizes.