I would like to introduce this page as my recommendation of IBM developerWorks' last week article:
CouchDB basics for PHP developers
CouchDB is "document oriented", non-SQL, and open source database system, and uniquely accesible via REST with JSON format. Damien Katz, who used to work in IBM Lotus, is one of the creators of CouchDB. That could be one reason that CouchDB and Lotus Notes/Domino is often compared. Actually, they seem to have common. They both are non-SQL database, and document oriented.
This page introduce basic of CouchDB, and APIs especially for PHP developers with sample. This could be nice "getting started" information for CouchDB with PHP.