CouchDB

Damien Katz showed off CouchDB. This is another example of a lightweight non-relational database that you can access through a REST API. The idea of Couch is to store self contained sets of information (like Business Cards which don't contain foreign keys) that they refer to as documents. The database stores your info in JSON (similar to XML) and you access everything over HTTP. Their approach to viewing, collating and aggregating data is novel. They pull the data out as a flat file and use a JavaScript implementation of Google's MapReduce to reduce (query) the large set down. Couch is written in Erlang which is starting to gain some popularity as functional programming is seeing a small resurgence. Erlang allows them to be highly scalable + they have built in strong replication. Because it's flat it allows full-text searching out of the box without having to teach the indexer what the objects are.

Couch is still in the experimental stage but it's interesting to see innovation happening outside of the relational database model.