I'll start the thread...
Was going to say Arapahoe county, however I think that Arapahoe county is gone from the GOP but hard to say. With the new development going on in the southeast part of Aurora it may be a close one to watch.
Weld county is growing rapidly in the 2000s, but has a large agricultural community. Has alot of Hispanics (Greeley) but not enough to make a big impact.
Adams county has a growing Hispanic community in south Thornton and unicorporated. Commerce City near Reunion has new development homes that balances out however.
Denver and Boulder county are DEM strongholds, so that's off the table. Douglas and Elbert county are strong GOP.
Jefferson county may swing GOP, but it's 50/50 with Golden and that city isn't exactly GOP friendly. The southern part of Jeffco is nothing like Golden and votes like Douglas county.
Not sure about Broomfield county...
Jefferson determines who wins the state in most cases. I'm actually secretely predicting that Arapahoe and Adams will swing WAY to the right in this next election. Those exurbs are pissed!! Some of those areas look like the economy just smashed the he!! out of them.
I think the entire state of New Hampshire is going to swing way, way to right in the next election. The registration change in 3 years is pretty staggering. I get the impression that either those entering New Hampshire are Libertarians who wont always vote with their pocket book(as L's usually do) and in 04, 08 swung to the Dems and now have come back home or the Dems that are moving their are quickly converted by the domestic population. Can't tell you which. But New Hampshire I suspect will be quite brutal for the Dems to watch how much it swings against them from years prior.
And I just haven't traveled to NC, FL, OH, and NV enough nor sat down and analyzed the states enough to be able to predict how counties would go. I can give you my summation of WI though!