NoSQL databases are some of the hottest topics in the IT industry in the moment. A beginner can easily feel swamped with the amount of documentation available. Since I am a beginner to NoSQL as well, I separated two links which I access every now and then:
A Visual Guide to NoSQL explains how the commonly used NoSQL offerings relate to CAP Theorem.
A Beginner’s Guide to NoSQL is an article, originally written for the Software Developer’s Journal, that explain the basics principles and ideas behind the NoSQL databases.