Google Spreadsheet or Google Sheets can help you collaborate with teammates! With their built-in chat and many more features, you can edit and complete projects together. With Google Script and functions, mathematical equations can be done within Google Sheets, just like Excel. A cheaper version, and arguably better version, why opt out?
Google Sheets is a spreadsheet application that runs on web browser. It doesn't require any installation or setup just a Google account and a modern web browser.
Visit http://sheets.google.com to try out now! Create a new spreadsheet and start playing around.