But more than a specific API, it would be cool if websites simply provided an XML(/JSON/etc) version for every urls. Eg, http://news.ycombinator.com/item.xml?id=955077 would return the data in this page in XML format. This would be pretty simply to create (at least as read-only API), handle the situations where people resort to HTML scraping and effectively remove the need for API docs.
There's also RSS, but all of these provide access to mail functionality, while Gmail is a lot more than that. The uses I have in mind are closer to Google Labs' "Unsend", or having web service-like access to moving stuff around in gmail, creating alternate UI etc.
But more than a specific API, it would be cool if websites simply provided an XML(/JSON/etc) version for every urls. Eg, http://news.ycombinator.com/item.xml?id=955077 would return the data in this page in XML format. This would be pretty simply to create (at least as read-only API), handle the situations where people resort to HTML scraping and effectively remove the need for API docs.