I grew up playing Trivial Pursuit and other trivia games with my sister and I think that I have passed the fun along to my kids.
My son loves to play trivia games--he has 2 different kinds of Brain Quest card games, we will play Internet trivia games, and we have a trivia game on our Wii.
We watch "Are You Smarter Than a Fifth Grader?" and other shows like it.
My DD is only 5 but does her best to jump in and answer the questions.

She does one heck of a job guessing, too!
What trivia games/shows does your family like?