Good intro material about Hadoop (and a bit of Hive):
One design pattern that both Google and Facebook share is the ability to distribute computations among large clusters of machines that all share a common data source. The pattern is called Map/Reduce, and Hadoop is an open source implementation of this. This article is an introduction to Hadoop. Even if you donʼt currently have a massive scaling issue, it can be worthwhile to become familiar with Map/Reduce as a concept, and playing with Hadoop is a good way to do that.
If you are new to map/reduce and Hadoop, keep also in mind that many NoSQL databases — Riak, CouchDB, MongoDB to name a few — are able to run natively map/reduce jobs.
Getting Started with Hadoop originally posted on the NoSQL blog: myNoSQL