Well, if you're counting states, I was in Los Angeles in 2008. But that doesn't really count, cause my plane touched down on LAX around 8AM and i was on a plane back home at 10PM the same day. Quite frankly, I couldn't wait to get the hell out of there.
Also, I was in Atlanta and San Francisco in 2010. That time I stayed for a few days.
I counted States because I figure the majority of posters are Americans and it would be useful to distinguish us. I certainly don't think it's necessary for foreigners to count the States they've been to (just like I don't need to count Canadian provinces or Mexican states).