Great review article:
"In this article I digested a number of MapReduce patterns and algorithms to give a systematic view of the different techniques that can be found in the web or scientific articles. Several practical case studies are also provided. All descriptions and code snippets use the standard Hadoopâs MapReduce model with Mappers, Reduces, Combiners, Partitioners, and sorting. This framework is depicted in the figure below." (from Highly Scalable)
Worth reading if you are interested in how Hadoop and friends might apply to the problems that you are trying to solve: "MapReduce Patterns, Algorithms, and Use Cases"