DC has a good group as well with the Barra and the Screaming Eagles.
Metro and New England are okay, but nothing spectacular
IMO. Same goes for LA. RSL was fairly good for a 1st year group, but I'd like to see more. San Jose had a good supporters section, but they were about the only people going to the games.
Columbus had a good group in the V-Army that I think was ground down into apathy by having Coach Clueless kept around for so long. (that and having so much of the group being OSU students who graduate and leave or go home in the summer)
KC and Colorado...do they even have supporter groups? You could probably ask the same of Chivas USA.