I vote for Fenway Park (Boston) and Yankee Stadium (the Bronx ) among the classic still standing ballparks, while SFO and CLE would rank with DEN or DAL as new ones. (We could always consider visits to the sites of those ballparks which are no more: Ebbetts Field, Tiger Stadium et al when visiting those cities.) Perhaps we could do an east coast/west coast mini-tour, then head inland. (DEN would give us a chance to drop in on the House of Cards, too.)
I trust everyone knows about
http://www.baseballparks.com the best site for exploring the whole subject, plus links to just about every other site related to classic baseball. Anyone catch the Food Network had a special on ballpark food this past weekend?