Back on labor market after 5 years, what's next?

I'm back on the labor market after 5 years in the bay area. I'm looking for new opportunities but I don't really know how to find interesting ones.

I'm exceptionally good at solving complex problems, implementing/creating new algorithms to solve them.

What companies (still) have nice challenging problems to solve ? Where should I be looking ?!

eg: I don't want to build your next statistic dashboard