Numbersearches! Choose a number, write it in the middle box. Kids search vertically, horizontally and diagonally to find addends that equal the number. In 2nd grade we use this for numbers 7-20. It's a great "sponge" when you have a few spare minutes! I put a blank copy on my Pinterest page.
In the news magazines for box in your classroom library...You don't have to teach current events to make students knowledgable about what's going on in the world. This would be a great option for when students finish an activity early.