The unAPI Server is a WordPress plug-in implementing the final version of the unAPI specification, “a tiny HTTP API for the few basic operations necessary to copy discrete, identified content from any kind of web application.” Read the final version of the unAPI spec at http://unapi.info/
The server provides records for each WordPress post and page in the following formats: OAI-Dublin Core (oai_dc), Metadata Object Description Schema (MODS), SRW-Dublin Core (srw_dc), MARCXML, and RSS. The specification makes use of LINK tag auto-discovery and an unendorsed microformat for machine-readable metadata records.
The plug-in lives here: http://www.lackoftalent.org/michael/blog/unapi-wordpress-plug-in/
This is my first WP plug-in, so any feedback is appreciated. :)