Arithmetic Four is a Connect Four variation where you have to answer an arithmetic question correctly before you can play a chip. You get to choose the category, the operation, the difficulty level and the time limit.

http://www.shodor.org/interactivate/activities/ArithmeticFour/?version=1....

Arithmetic Quiz is similar but without the Connect Four interface.

http://www.shodor.org/interactivate/activities/ArithmeticQuiz/

The classic Connect 4 game, but students have to first correctly evaluate the numerical expresson before they are allowed to drop their chip.
http://www.shodor.org/interactivate/activities/OrderOfOperationsFou/

This virtual manipulative uses plus-minus chips to demonstrate adding positive and negative values.
http://nlvm.usu.edu/en/nav/frames_asid_162_g_3_t_1.html?open=instruction...

The goal of this puzzle is to put three numbers inside of each circle so that they add up to 0.
http://nlvm.usu.edu/en/nav/frames_asid_122_g_3_t_1.html?open=instruction...

This J virtual manipulative uses plus-minus chips to demonstrate adding positive and negative values.
http://nlvm.usu.edu/en/nav/frames_asid_161_g_1_t_1.html?open=instruction...

This virtual manipulative allows the user to visualize the product of two integers.
http://nlvm.usu.edu/en/nav/frames_asid_322_g_1_t_1.html?open=instruction...

http://www.explorelearning.com/index.cfm?method=cResource.dspView&Resour...

A Gizmo* to teach adding and subtracting integers using a number line.

* You can use a Gizmo for up to 5 minutes per day for free. If you want to use it for a longer period, you must purchase it.