If you have young students or preschoolers let them play with this.
You can go to the iTunes store and download it or you can go get Crewton Ramone's Absolutely Amazing Addends here.
Put it on your iPhone or play it on your iPod Touch, Mac or PC, soon it will work on iPad too but we need to make some upgrades in especially the graphics which make my kids laff but need to be more "professional" this is aimed at ages 3 to 7, of course older kids can use it but it really is made for the wee ones.
As I was making this post a boy who is just a week away from 4 came in and asked me if he could play...and I had to send him off to watch The Aristocats so I could finish.
It should hold their attention for a few minutes a day until they have mastered the addends for 9 and 10. My three and five year old enjoy it...need to get some video of them playing with an actual iPhone or iTouch and put it here. It's fun. Simple, silly, fun.
Here are actual children playing with it: (Their names have been changed to protect the innocent).
Take it away and let them play again another day...always keep them wanting more. Don't let them goof around with it until they are bored, especially now when it only has a few features...
More on addends here and here. Basic addition lessons here. Article on the importance of addends here.