Well this site is a ladder site where there are rankings and you can simply just add members on a team. It's very easy. Also make sure to display your Friend Code(s) on your blast message. This is kind of a new site and I want to make the Mario Kart Ladder active because I don't really know any other ladders as simple as this. I like Gamebattles, but they wont put on a team ladder. This site is TEAM LADDER.

Here's the link to the Mario Kart Arena:

http://gamerzcentral.com/standings.php?ladder[id]=124&ladder[unranked]=1

Yeah, there are only a few teams signed up now, but you guys can make it active. =)
First create an account and easily join a ladder.