A new GData API is available today, for spreadsheets in Google Docs & Spreadsheets:
"Now there is the possibility of getting a feed listing your updated spreadsheets, and since there is more than one way to think of a spreadsheet, we give you two different feed schemas for viewing. A worksheet could be viewed as entries of individual cells or as a list of rows similar to a database table."
Check out the GData blog for further details!