"We definitely want to build out APIs, especially for the spreadsheets side, as spreadsheets are more data-oriented, but maybe also for he word processor," Google product manager Jonathan Rochelle said. "People will be able to do mashups with our tools for other things, and not be stuck behind our dev cycle for everything they want."
Developers would be able to use the API to build software for pushing local content to the hosted services for collaborative work, then retrieving it later, by way of example, Rochelle said.
"If I've already got data somewhere you can't really rely on manual cut-and-paste to make it collaborative. Imaging pulling data from any application you've already got in use... you get that data over to the hosted app, make it collaborative, then bring it back... that's what we'd like to enable at some point," he said.
As for Google APIs in general, as of now, there are these 12 Google APIs listed here.