Before we started Two Bit Circus, I was exploring what to work on. It turns out the absolute best use of your time is not obvious. I asked the internet and learned there are catalogs of hard problems identified to promote our happy survival and best reduce human suffering and waste. I'm enclosing what I found in case anyone else is looking for pointers on what to do next.
http://science.energy.gov/ascr/community-resources/workshops-and-conferences/grand-challenges/
https://www.whitehouse.gov/administration/eop/ostp/grand-challenges
https://www.nsf.gov/cise/aci/taskforces/TaskForceReport_GrandChallenges.pdf
http://www.engineeringchallenges.org/
https://www.ycombinator.com/rfs/
http://a16z.com/2015/01/22/16-things/
https://en.m.wikipedia.org/wiki/Millennium_Prize_Problems
https://www.globalgiving.org/sdg/
http://mathworld.wolfram.com/UnsolvedProblems.html