It is possible to achieve results similar to those of using Excel with bundled, free, open source software and services.
Excelkurs Direkt courses can also be used for free Excel alternatives.
Excel Online is a stripped-down no-cost cloud-based version of Excel. Registration is necessary.
Staroffice Calc is a complete suite of programs matching the Microsoft Office applications for all Java platforms.
Apache Open Office Calc
Gnumeric is an Excel alternative for Linux. There is no automation support available.
WPS Office Spreadsheets
WPS Office Spreadsheets is not entriely free, but comes in an ad-supported version.