Many of the foregoing are great places to go, and I would gladly go there.
For my money, I would like to see the following, in no particular order. These could build on the existing eating tours:
Atlanta, GA (including Savannah and Mrs. Wilkes would be a bonus)
Milwaukee, Chicago (really, this seems too obvious, but all the more reason to go)
Texas–but not for BBQ, but for Tex-Mex or something similar.