Social choice, arrow's theorem and open problems ?
Your question is very well timed, because the most recent issue of the CACM has an article      that does exactly this: http://cacm.acm.org/magazines/2010/11/100640-using-complexity-to-protect-elections/fulltext

In brief, there's a lot of work by Conitzer, Tovey and others on the actual hardness, both worst-case and under distributional assumptions, of cracking voting mechanisms that are in principle breakable via Arrow's theorem.