Google’s spreadsheet will allow subscribers to share spreadsheets with others online, enabling all users to view and edit the data at the same time. Google are also supporting the import and export of data from Excel and CSV formatted files.
Google recently purchased Writely (article on Writely here) an online word processing software program, so it certainly looks as though Google believe there will be people wanting to ditch the Microsoft Office applications for a free online service.
At the moment Google spreadsheets is in limited trial. You can register for this free program on a first come first served basis here Google Spreadsheets.