Luajit projects useful for learning interop:
UFO Excellent examples of luajit ffi
https://github.com/malkia/ufo
Lua for Windows:
A huge array of interop libraries for windows. You can make almost any application using these.
https://github.com/rjpcomputing/luaforwindows
These projects provide a huge array of samples and libraries for people to learn Lua and Luajit with. Highly recommended to new Lua users.