GData gives access to Apps, Base, Blogger, Calendar, Code Search, Notebook, Picasa Web Albums, and Spreadsheets. List is growing.
A protocol for reading and writing structured data over HTTP based on REST. A lot less complex than SOAP.
Atom Publishing Protocol uses HTTP GET to get feed data, HTTP POST to add a new entry, HTTP PUT to edit and HTTP DELETE to delete an entry. Interesting.
Authentication works through ClientLogin (highly trusted applications) and AuthSub (for less trusted web applications).
AuthSub is works like Flickr’s authentication model as well.
