The Google Spreadsheet team has added some new features to the online tool. Chief among them is the integration with Gmail and Calendar address books so that one collaborate more easily when sharing spread sheets. Google Spreadsheet now allows the author to share that spreadsheet publicly. Previously one was able to share a spreadsheet only by private invitation.
Another key feature is support for two popular formats, Adobe Portable Document Format (.pdf) and Open Document Format (.ods). This support is a great help to those like me who do not use Microsoft Office for document creation and those who prefer not to share editable document formats.