I always write the objective/target with the kids as we begin each lesson. My district has encouraged this strategy for the past few years and it is now listed as part of the lesson on our new evaluation tool. Since I was HORRIBLE at remembering to do this, the brightly colored circles on the board provide a nice visual reminder. I wish I had a picture of my classroom to share!
I am sure there are many other ways they can be used (maybe on a table as a space to practice skills during a small group?) Hmmm... I'll have to think about that!!