NoSQL
It’s getting bigger and bigger all the time. Your relational database sucks.
http://blog.oskarsson.nu/2009/06/nosql-debrief.html
http://incubator.apache.org/cassandra/
http://labs.google.com/papers/bigtable.html
http://s3.amazonaws.com/AllThingsDistributed/sosp/amazon-dynamo-sosp2007.pdf
I’m hopefully behind on my knowledge.