Using Lua in Arduino project I want to write code for my Arduino in Lua. Where I can find the necessary (pins) I/O lib and examples for Arduino IDE?
UPD: I've got arduino mega with many memory.
Lua is an interpreted language. That is, the compile phase turns Lua source code into intermediate "pseudo-code" which the Lua interpreter then runs. It doesn't compile into machine code, and therefore there is nothing that could be uploaded to your Uno as a "hex" file.

In any case, with only 2 KB of RAM, it wouldn't be very practical to attempt to run Lua on a Uno. I like Lua personally, but running it on the (AVR) Arduinos just isn't practical.