Anti RDBMS : a list of distributed key value stores
http://www.metabrew.com/article/anti-rdbms-a-list-of-distributed-key-value-stores/

David M. from Boxed Ice, post a good paper about migration from MySQL to MongoDB
http://blog.boxedice.com/2009/07/25/choosing-a-non-relational-database-why-we-migrated-from-mysql-to-mongodb/

Very interesting paper from GigaOm : Is memcached a good or bad sign for MySQL ?
http://gigaom.com/2009/05/17/memcached-and-an-ailing-mysql/

Gigaom : Why storage needs more structure ?
http://gigaom.com/2009/03/22/why-storage-needs-more-structure/

Some notes on distributed key stores
http://randomfoo.net/2009/04/20/some-notes-on-distributed-key-stores

Projects :

Voldemort
http://project-voldemort.com/

Open Neptune
http://openneptune.com/

Hypertable
http://hypertable.org/

MongoDB
http://www.mongodb.org