I have a goal to visit every ball park in the major leagues. I'm halfway through, right now.
Here are the teams I've already visited: Orioles, Yankees*, Red Sox, Rays, White Sox, Royals, Twins*, Braves, Marlins, Mets*, Phillies, Nationals, Cubs, Cardinals*
*this means I've seen the old stadium where they used to play, and the one they're at now. Meaning: both old and new Yankee Stadium; Busch Stadium II and III in St. Louis; Shea Stadium and Citi Field for the Mets; and the Metrodome and Target Field for the Twins
Ones I'm going to this year: Mariners, Diamondbacks, Angels, Dodgers, Athletics, Giants, Padres, Pirates
And those which I will have left: Blue Jays, Tigers, Rockies, Brewers, Rangers, Astros, Reds, Indians
How am I getting there? In some cases I take an organized tour, because there are some ballparks (like Dodger Stadium) where you have to drive to get there, and no way am I wasting my vacation time driving. Plus the thought of driving in California scares me - I know for a fact I'd get lost. But in cities like New York, Chicago and Boston, which have mass transit, I can go there alone.
Once I get all of these places visited, I can go back and revisit the ones I like the best. My favorite non-NY ballparks - the Yankees and Mets are my favorite teams so I am biased
- are definitely Fenway Park (Red Sox) and Camden Yards (Orioles). I'll probably spend two weeks on those!