#Skhematos
Skhematos.com will eventually host this webapp, which will provide an interface to do manual data entry on a variety of metadata databases, as well an API for other external/third-party applications to make use of (including but not limited to: Plex, MediaBrowser, and whatever they're calling XBMC these days.)
I'm making the code public in the slim chance that it actually helps someone else.
John O.