Champions League, G14, blah blah blah.
The guy behind 200% (usually a good read) has come up with his list of the "20 most important clubs in the world". There's a few that aren't that surprising - Ajax, Boca Juniors - but a load that are (New York Cosmos, Enfield Town etc.) Full list and reasons at http://www.twohundredpercent.net/?p=1219
So, who would be in your "most important clubs in the world" list?