We read a bunch of books on baseball and I read some of the baseball-themed poems out of Jack Prelutsky's new anthology, Good Sports: Rhymes About Running, Jumping, Throwing, and More. Incidentally, I remember reading a blog post that totally trashed this book (and sports poems) in general, because they are "all the same."
Another choice was The Jungle Baseball Game by Tom Paxton.
The big hit of the event was a nice, long game of frying pan baseball. The player (who was actually a pitcher, so this was especially funny to watch) used a frying pan to bat the "ball"--a bunch of grocery bags rubber-banded together--while the kids tried to catch it with pots.
Following that, we made fireworks in a glass (Fill a tall, clear drinking glass with room-temperature water, leaving about an inch of space at the top. Pour 3 tablespoons of vegetable oil into a smaller glass and add 1 to 2 drops each of red and blue food coloring. Gently stir the mixture once or twice with a fork to barely break up the beads. Pour the shorter glass into the water glass and watch. It takes about 30 seconds for the beads to burst through the oil, releasing miniature fireworks. We set three glasses of fireworks on the floor and let the kids stretch out in a circle around them to watch. This is an idea from the July/August 2007 issue of Family Fun magazine (last page).)
For a craft, we made ball-shaped baseball cards and wore them around our necks.