Good Core Exercises?!?!

Today is my "rest day" and I would like to do some exercises to strengthen my core muscles. I know some of them (planks, sit-ups, crunches, "V" ups, opposite supermans, etc). I was wondering what are the most effective exercises to improve and strengthen my core muscles for running. Is there an exercise better than another? Is there another exercise that I should know about and try? Any advice on this subject would be awesome and very appreciated since I am not sure what is best for me to do. 

Thanks for reading!!