The thinking at Big Think is big indeed. This blog and video site covers, well, the world: arts, business, science, history and much more. Resident big thinkers such as futurist Ray Kurzweil and distinguished guests tackle the topics seriously, and counterintuitive notions and outright heresy are welcome. (One post speculated that there's a 20% chance that we're all part of an elaborate computer simulation from the future.) It's a great place to go to challenge your preconceived notions and recharge your mental batteries.