Hardware for attiny chips to work with arduino IDE.
To work with Arduino IDE and Attiny download 'hardware' folder and paste it in your sketchbook folder, restart Arduino IDE and there it should be Attiny under boards.
I have found this setup on : http://elabz.com/arduino-shrunk-how-to-use-attiny13-with-arduino-ide/
and these files I've downloaded from the link on the link above from comments
nihaopaul: November 27, 2012 at 1:34 am here are a few cores for your arduino..
download this file: https://docs.google.com/open?id=0B0N5FlIrsEEwZnN5ZlZ5NjVSWG8