Here are three quilt block tutorials that I put together for the Boston Modern Quilt Guild BOM.
These tutorials all have improvisational techniques, but they also let you be a little precise if you want to be.
This tutorial lets you practice curved piecing: Curves Ahead
With this one you can try paper piecing without worrying about things being too perfect: Playing with Paper
And this tutorial lets you improvise with strips of fabric: Fenced In