A Group of One by Rachna Gilmore. This site has excellent notes on the book; scroll down to the bottom for notes. The author has a very good website here.
Sliding Into Home by Dori Hillstad Butler. After she moves with her parents from Minneapolis to a small town in Iowa, 13-year-old baseball fanatic Joelle Cunningham cannot believe that she's not permitted to play on her new middle-school's baseball team. Convinced that girl's softball is not an adequate alternative to baseball, she starts a one-girl campaign to change the small town's rules, and her protest eventually expands into a community conflict that is televised on the local news. Determined Joelle is a fine protagonist. Readers will be caught not only by her drive to play ball and her willingness to take risks but also by her passionate commitment and the broadening vision that doesn't allow her to settle for just being the one female on an all-male team. Although there is only occasional play-by-play coverage of baseball games, the well-paced plot will engage readers, who will be moved by the story of a young teen who stands up for what she believes and goes after what she wants. Booklist.