Google Reader API Documentation
There isn’t really any such thing as Google Reader API documentation.
But I do have a PDF document that Nick Bradbury wrote up when we were switching FeedDemon and NetNewsWire from NewsGator syncing to Google Reader.
It’s from 2009. Parts of it are surely out-of-date (authentication, for sure), and it was written with the expectation that the reader is familiar with NewsGator syncing.
Nevertheless, in the spirit of Marco’s baby steps toward replacing Google Reader, I present it (with Nick’s permission) in case it’s useful to anyone: