I first learned about Petr Mitrichev the past year when he won 2011's Facebook Hacker Cup. He's a Google developer leading the current competitive programming challenges. He also keeps an interesting blog at petr-mitrichev.blogspot.com where he talks about algorithms and sometimes challenges his readers with some problems.
I also found some interesting reading material if you're into competitive programming. Codeforces has a great post about Sao Paulo Training Camp 2010 containing his solutions to problems and some video explanations.
Update March 2013: He came up on top at 2013's Facebook Hacker Cup as well. This is guy is amazing :)