Maine and Georgia are really the only two obvious ones, if you ask me.
Really it's Georgia on a different level than everything else, but Maine is the closest Dem analog. New England whites are just so different from non-New England whites, and I believe there is a pretty large age-gap in favor of the dems, so I think they'll remain competitive even as the state becomes bright purple due to demographics.
Georgia Republicans just have no chance under the current coalitions. Next Virginia.
Eh, I don't think GA will turn into Virginia (which will be safe D in 5 years and start voting like Illinois or New Jersey) but it will be lean D, like New Hampshire is now.