Because Firefight mode doesn't have a Matchmaking system, I put together a website called TeamFirefight.com to help players connect with one another in real time. Our Matchmaking Messenger is a browser-based IM service that you can open up and find other people ready to play Firefight whenever you are. We've also got a forum to discuss all things Halo and video game related on.
www.TeamFirefight.com
Join up, and help spread the word!
www.teamfirefight.com - the Matchmaking site for Firefight!