MicroATX would be fine for most people, especially since most of us only have one add-in card, which is our graphics card. Z68 is only worth the cost of you'll use the extra features. I have a P67 board, and am not really missing out on anything.
To the OP, just go to Newegg as mentioned, and set your search options for what you want. It will refine the list down to give you a few choices and consider. Stick with a known, trusted brand, and you'll be fine.