QuizUp - QuizUp gives you the opportunity to test your trivia skills against friends and strangers throughout the world.
Xmind - Xmind is a brainstorming and mind mapping application.
A Google a Day - Online trivia game where you use Google's search to answer questions as fast as you can.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Trivia Crack Kingdoms - The amazing quiz game that lets you test your knowledge and challenge your friends to see who is the smartest. Developed by Etermax
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.