I'm not really big on football, and I don't normally follow it.
However, my Dad does, and he is a fan of Manchester United, so I normally consider them my team.
Furthermore, my Uncle and cousin are avid Chelsea fans (although I think they used to be Arsenal fans or something, before Chelsea got good, the posers), so we're quite happy to rival them.
And then I suppose the only other team I care for is the national England team, although I don't think we're all that great.