My notes used to train the Mexican Mathematical Olympiad were published in Spanish and English. They contain the tools needed to solve any combinatorics problem from a mathematical olympiad.
"Gerrymandering, Sandwiches, and topology" Notices of the AMS 64(9) pp.1010-1013.
The notices article was highlighted in "october's spotlight" of the AMS math grad blog.
Using Ham Sandwich cuts to gerrymander
I was recently made aware of a similar application of fair partition results to gerrymandering by Macarthan Humphreys. His paper (which also has more references on the subject) can be found here.
"El principio de las casillas" (in Spanish, "the pigeonhole principle"). Tzaloa 2010 (2) pp. 1-6