I think I've settled on my two ballparks I'm travelling to see this year:
Baltimore in June (Yankees series)
Kauffman in August (Twins series)
Orioles and Royals fans, whats good to see in each respective city?
Well, for one thing,
do not fail to go to the Negro Leagues museum before you leave KC:
Also, prepare to eat some BBQ. I recommend going to one or more of the following:
-Arthur Bryant's at 16th and Brooklyn (the granddaddy of all KC BBQ),
-Gates (the other granddaddy of KC BBQ),
-OK Joe's (the one that everybody likes the best these days. Definitely new school, they've only been around since the 90's; famously located in a gas station)
-Jack Fiorella's Jack Stack BBQ (fancier sit-down BBQ)
...and there are TONS of other great places, too, but those four are generally considered to be the top-tier.
If you care about soccer even a little bit, you should catch a Sporting KC game while you're in town, if possible. It's an unbelievable atmosphere that I really think few other sports teams can match.
There's more to recommend, too, depending on what part of town you wind up staying in.