This activity could be used for any addition but we are continuing with number 2 right now. The boys are very comfortable counting it in their head by the end of the week, it's amazing!
Take two dice. Leave one sitting untouched on the particular number you are using to add (in our case #2) and throw the other dice.
Then add both numbers. To make it more fun we used blackboard this time. The boys like to erase and rewrite, which is fine with me because it helps them practice number writing. You can also use a regular paper or erasable board.