The Common Core has done one thing if it has done nothing else and that is to stimulate growth in the educational section o the public sector. A Google search of "Common Core math" yields "36,200,000 hits in 23 seconds". Many, many of these are publishing company's attempts to cash in on the need for new materials to meet the demands of the soon-to-be required Common Core math (at least in those states that have signed up).
Over the past year or so I have been bombarded with websites offering all kinds of things usually promising to make my job easier ( I wish they would promise to make it better) Every-so-often I poke around on my own looking for something I can use i my courses and recommend to colleagues. Here's one that I find quite amazing because it is so simple and straight forward and the math is absolutely wonderful. The work-cards and images for arrays are terrific and are so much better than the rectangles one so often sees that I find confuse arrays with area.
How many eggs are there? A student who understands the concept of the array as multiplication will say 4 x 6 while the student who doesn't will count them one ob one.
Here is the K-5 Math Teaching Resources; it really is worth a visit. I wish I knew who the authors were though.