This is the IRremote library for the Arduino.

To install, move this directory to:
arduino-00nn/hardware/libraries/IRremote

I.e. after installation you should have files such as:
arduino-00nn/hardware/libraries/IRremote/IRremote.cpp

If you're downloading from github (http://github.com/shirriff/Arduino-IRremote), click on the Download Source button in the upper right and get a zip file.  Unzip it, and move the directory as described above.

For details see http://arcfn.com/2009/08/multi-protocol-infrared-remote-library.html

Copyright 2009 Ken Shirriff