A good base from which to start I have found is RASPBIAN which can be downloaded from http://www.raspberrypi.org/downloads/ the latest version at the time of writing this page this is 2014-09-09-wheezy-raspbian.

    Having downloaded RASPBIAN, the first task is to unzip the file leaving you with the disc image 2014-09-09-wheezy-raspbian.iso

HOME