Google Docs Data APIs

http://groups.google.com/group/Google-Docs-Data-APIs

Google Spreadsheets Data API  [Java, .NET, Python, PHP]
The Google Spreadsheets Data API allows client applications to view and update Spreadsheets content in the form of Google Data API feeds. Your client application can request a list of a user's spreadsheets, edit or delete content in an existing Spreadsheets worksheet, and query the content in an existing Spreadsheets worksheet.