QuizClash - In QuizClash, you can challenge your friends or random opponents to a game of trivia.
Startup School - How to start a startup, by Y Combinator
Trivia Crack - Produced by Etermax, Trivia Crack lets players answer trivia questions and compete against other people on mobile devices.
YC World - Explore Y Combinator companies by country
A Google a Day - Online trivia game where you use Google's search to answer questions as fast as you can.
Y Combinator Companies - Interactive list of all 1000+ YC companies