One of the things I love about fellowships - is joining a team (for a game I like), and then being on that team in a "Site Team Tournament" against other fellowships.
There are a few different types of fellowships.
There are "Big" fellowships, with a lot of people - and a lot of people on their teams. IN MY OPINION, It is nice to join those fellowships, but NOT to join their teams. A lot of site team tournaments limit the number of players a fellowship can send, so if only 5 will play, and there are 10 on that fellowship team - 5 will be left out. (So stay off those teams, and possible just play in their "Fellowship Tournaments" - which are tournaments just for those in that fellowship)
Small, Private, Chat - These are usually ran by a player, and usually just a select friends of that player belong. Possible not many tournament/games, but mostly around for the discussion boards.
Small, Tournament Bound - These usually try to get teams together for Site team tournaments or Fellowship vs. Fellowship tournaments. These are GREAT to get on since you will most likely play more and help out your team more.