Here is a very elementary video worth showing your students in K-2
grade.  It is definitely very elementary, but Sesame Street does an
excellent job discussing subtraction.  It is quite entertaining.

Save the planet by destroying the aliens quickly.  Students need to solve addition problems in order to fire the weapon.  This will surely improve their additions skills and fluency.

In this game, students can compete against each other online to see who can get their jet ski to the end, the quickest by answering addition questions.

This is a fun song to help review or introduce basic addition and also math vocabulary to younger students.

In this 1st-grade math worksheet, students will determine which the whole number is missing from a number sentence. First-grade students will get an opportunity to demonstrate how whole numbers relate to each other in an equation. These numbers range from 1-20 and the math worksheet in a Valentine style, both font, and imagery. There are 8 number sentence questions.

This website gives a great example of using the commutative and associative properties of addition using Skittles.  There is a video available that will help demonstrate successful implementation.

Students complete the 0 to 10 addition and each answer is given a "color" value.  The student color in the square the result is a lion.  Check out some other coloring math squares here.

This worksheet allows students to sort addition solutions into odd or even categories.

Practice your tens and ones place value with your students using this "Loopy" game.  Cut out the cards and distribute them to your students.  Each card should ends with "Who am I."  If done right all of your students would have a chance and answering a question and playing the game.

In this ABCMouse.com video students will get to see a fun video that includes 3 digit subtraction without the regrouping.  They show the grid method and the expanded method.