When I was young, "The Empty Barn", which was about a little girl who moved to a farm, and slowly filled her barn with animals. It allowed me to dream. Then I moved on to the "Little House" series, which I think helped to stoke a love for American History. I also enjoyed "Harriet the Spy", A story with a strong female lead, and later, "A Wrinkle in Time" because it allowed me to escape, and the message that love can trump evil is pretty darned powerful.
Later, "To Kill a Mockingbird" because Atticus Finch was quite a role model, a model that I try to live up to, but I must admit I fall short of.
The Octavia Butler series "Parable of the Sower" etc caused me to look at life and the world in a whole different way. There are many others, but these jump out at me today. Tomorrow, it might be a slightly different list :-)