Approximation algorithms, algorithmic game theory, and networking.
Network effects of risk behavior change following prophylactic interventions with V.S. Kumar, R. Rajaraman, and R. Sundaram PLOS ONE 2013
On the Complexity of Information Spreading in Dynamic Networks with C. Dutta, G. Pandurangan, R. Rajaraman, and E. Viola In proceedings of SODA 2013 [pdf]
Existence Theorems and Approximation Algorithms for Generalized Network Security Games with V.S. Kumar, R. Rajaraman, and R. Sundaram In proceedings of ICDCS 2010 [conference version] [full version] [presentation]
Feige and Krauthgamer published a paper on Bisection Problem in 2000, which gives a combinatorial algorithm with polylogarithmic approximation ratio. The algorithm contains lots of technical pieces, and is hard to keep all of them in mind or understand the intuition behind them. I wrote a sketch, trying to give a high level structure of the algorithm and some intuition. (In 2008, Racke improved the approximation ratio to O(log n) as a result of his Racke decomposition)