Microsoft Office Excel - Microsoft Office Excel is a commercial spreadsheet application.
EtherCalc - EtherCalc is a web spreadsheet.
Google Sheets - Synchronizing, online-based word processor, part of Google Drive.
FlexiSheet - FlexiSheet is a multi-dimensional spreadsheet in the spirit of Lotus Improv.
LibreOffice - Calc - LibreOffice Calc is the spreadsheet program you've always needed. A fork of OpenOffice.
Gnumeric - Gnumeric