Relevant links:
http://riakhandbook.com
http://www.percona.com/doc/percona-toolkit/2.0/pt-online-schema-change.html
http://blogs.innodb.com/wp/2011/04/nosql-to-innodb-with-memcached/
http://yoshinorimatsunobu.blogspot.com/2010/10/using-mysql-as-nosql-story-for.html
http://blog.creapptives.com/post/14062057061/
http://robots.thoughtbot.com/post/13829210385/