Good articles on NoSQL

http://en.wikipedia.org/wiki/NoSQL

http://en.wikipedia.org/wiki/Document-oriented_database

http://jcsummanen.wordpress.com/2012/07/11/mongodb-overview/

http://searchhub.org/2010/04/30/nosql-lucene-and-solr/

http://stackoverflow.com/questions/3215029/nosql-mongodb-vs-lucene-or-solr-as-your-database