I just found the American Council on Exercise site – it’s a great resource! Their “exercise library” (click on GetFit, then select exercise library) can be searched by target body part, experience level, or filtered by what kind of equipment you have on hand. There seem to be a lot of options for “no equipment”, too, which I particularly like.
I’m intrigued by this Core Workout plan, too… it’s got animated photo examples of each exercise, with good directions. I’ll let you know if I give it a try!