Jaysus! Piss up....brewery.
The best way to organise this is for everyone interested in joining for FIFA10 to add their PSN ID and we'll edit them into one post. People send out friend requests mentioning the caf.
When someone is online and is playing FIFA they can create a new text chat session, call it Caftard FC and invite people to it as they log on. This can be run 'behind' FIFA and overlays some of the message received so you don't have to be sat in the changing room doing feck all whilst waiting for team-mates and is also slightly useful during a match for the folks that don't have a mic. It can also be saved so that you can quickly join it again to check if any players are online the next time that you log on.
Once there are three or more people in the chat room everyone jumps into the dressing room and away we go. As more people come online they join, they can see who is online and playing club, they can ask how long of the current game is left etc. etc.
Simples.