I've been playing with CouchDB a little recently. Its a "schema-free document-oriented database", which sounds pretty weird when all you've ever known is relational databases. At work, we're considering what architecture we want to go with for a new product that needs to be very flexible - the users need to be able to add fields, remove fields, and do all sorts of crazy things with the application. One of the options we have, is to use something like CouchDB to be able to create an uber-flexible...