A standalone, portable Ada package for producing Excel spreadsheets
Javascript plugin to create web-based tables & spreadsheets
C++ library for creating XLSX files for MS Excel 2007 and above.
Python spreadsheet application
Lays out dependencies (links) between Excel files in a visual graph
Compares two Excel files on a cell-by-cell basis and dumps differences
C++/C library to construct Excel .xls files in code.
OTC Trading Network
an embeddable spreadsheet for your web application
Small, fast Java library for reading and writing CSV files