I enjoy the trivia sessions immensely. I can't always be online then, and I am quite dreadful at some. But here are a few ideas:
--American History
--European History
--Fantasy Books
--Flowers or Trees or Botany
--Rock Music
--Planet Earth
--Harry Potter
--Lord of the Rings
--Biology
--Health
--Exercise and Sports
--Oceanography
--Civil War
--Revolutionary War
--Languages
--Art
--Astronomy