The challenge board project aims to be an open source ladder system that can be used to run any number of competitive events. If you can compete against a single an opponent, you can can have a challenge board.
Competitors can move up and down on the board by playing amongst each other and submitting the results. Standings are currently calculated using a standard Chess ELO algorthym.
Recaptcha keys: http://www.google.com/recaptcha. Recently I've needed to add protection against spammers, so Polite Recatpcha is now being used. You can develop on localhost, but moving to production will require a set of keys.
- Demo site on AppHarbor: http://challengeboard.apphb.com/
- Trello Board: https://trello.com/board/challenge-board/50e88cfdcba7353c10002706