You can make an obstacle course out of pringles cans, or just about anything, and weave through them. First, set the objects far apart and gradually move them closer and closer together. You're weaving and turning abilities will definitely get better.
We've been told it's good practice to weave though once, then go back through and pick them up, though we never managed to do that.
Another obstacle course idea to try is drawing a little "maze" of sorts out of chalk and see how closely you can follow the line. You can make the course with two lines and try to ride between them, or one line and try to ride on it.