Your calculator is broken but you can still get the answers... Six levels from easy to very challenging. A very motivating activity.
http://www.subtangent.com/maths/games-dl/broken-calculator.zip

The Countdown Game is a great way to review Mental Computation and the Order of Operations. Highly recommended.
http://www.subtangent.com/maths/games-dl/countdown.zip

Numbers and Letters is a variation of the Countdown Game that has additional controls for classroom use.
http://www.subtangent.com/maths/games-dl/numbers-and-letters.zip

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.

This is one cool calculator:
http://www.metacalc.com/#/large/

Mad Minute is a quick warm-up and review, typically taking one to two minutes. This MM reviews mental percent questions. You can use this as a template to create more Mad Minute pages. If you do, please submit them to the website!

Virtual fraction bars. They can be used to teach or reinforce fraction concepts such as equivalent fractions, or addition and subtraction of fractions.