EtherCalc - EtherCalc is a web spreadsheet.
SSuite Axcel Professional Spreadsheet - This powerful and professional spreadsheet has all the tools you need to calculate, analyse, summarize, and present your data in numerical reports or colourful graphics.
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.
Keikai - Effortlessly Build Spreadsheet-driven Web Apps
Pyspread - pyspread is a non-traditional spreadsheet application that is based on and written in the programming language Python.