SQL and NoSQL: When to use what for my App?

RDBMS (SQL) and other structured storages (NoSQL) explained by Martin Fowler (http://martinfowler.com/nosql.html):

Also interesting:

MapReduce easily explained

Confused about the MapReduce algorithm for parallel processing of "Big Data"? It's an easy concept, e.g. used in Hadoop: http://java.dzone.com/articles/confused-about-mapreduce