AntLog is a tool I have written to automate Peter Waller's double-elimination sheets.
It is a set of macros in an OpenOffice.org spreadsheet template. It will run on any version of OpenOffice.org or LibreOffice from 2.3 onwards. OpenOffice.org and LibreOffice are available for Windows, Linux and Mac OS. AntLog supports competitions for 8 to 128 robots.
I have also drawn up a set of charts to exactly match AntLog. Handy for a paper back-up or can be used in their own right as a low-tech solution.