Lua

A simple, powerful scripting language

Free. easy to use and lightweight code editing program for Mac by Li Jianyu

This internal development environment is open source, free to use, and supports a few different languages

A fully rounded development platform for Android that includes an editor, emulator, and code templates

Add a whole host of math functions to your programs with one of the most popular Python libraries

A free development application for Mac that allows you to compare file differences