Abs exercises ... but not planks

I am looking for a list of ab exercises ... but not planks. I discovered that I cannot do planks because I have arthritis in my right foot and balancing myself with my feet as shown in "how to do a plank" photos is agonisingly painful. I also can't do push-ups for the same reason.

So, if you know of some good websites with other ab exercises, I'd like to see them.