LuaCalc is a simple program for manipulating spreadsheets. It aims to be small, fast, simple and extendable. There is a wxWidgets user interface allowing copy/paste, sorting and redo/undo, while the backend is written in lua 5.1 and uses many features unique to lua.
Spreadsheet functions are just plain lua functions, so more can be easily added. The lua code can be run with the standard lua interpreter, which allows easy scripting of luacalc files.