Go tournaments are generally run using a McMahon draw. There are several programs which can be used to control such a McMahon tournament. Some of these are listed in the BGA Software Catalogue.
The draw program recommended by the BGA for use in British tournaments is GoDraw V6, written by Geoff Kaniuk. It runs under Windows.
If you run your tournament using GoDraw, there is a streamlined procedure for submitting your results to this web site and the EGF ratings.