Older Projects
My first OOP applications were developed in C-sharp. My goal was to make application that can be helpful and solve real life problems, not just some meaningless uses of theory. I found very good book for learning C# by developing small games. This book explained very well the objects, classes, delegates, lambda expressions, interfaces etc.
Sure, first applications are never developed perfectly and there are some things which I would do differently now, but the best way to learn is simply do.