A simple but effective idea, and nicely implemented!
Students can paint in a given percentage on a 100 grid.

Or a teacher could paint in a percentage and camera it to a page of an IWB document.
http://www.oswego.org/ocsd-web/games/PercentPaint/ppaint.html

Students play a version of Connect Four, gaining the chance to place a piece on the board by answering questions about simplify fractions, converting fractions to decimals and percents, as well as algebra questions involving fractions.

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

Click on two cards to turn them over. If they match, they are cleared from the board. If not, they remain on the board. How many turns will it take you to clear the board?

http://www.interactivestuff.org/match/maker.phtml?featured=1&id=9

Can you match the fractions, decimals or percentages pairs?
http://www.bbc.co.uk/skillswise/numbers/fractiondecimalpercentage/compar...

From the website: Here are two activities to see what percentages look like. In the second one you can compare percentages and fractions.
http://www.bbc.co.uk/skillswise/numbers/fractiondecimalpercentage/percen...
http://www.bbc.co.uk/skillswise/numbers/fractiondecimalpercentage/percen...

A collection of matching games, including multiplication tables, addition tables, equivalent fractions, and fraction-to-percent conversions. These are flash files.
The answers are randomly placed so each game can be used over and over.
http://www.subtangent.com/maths/games-dl/matching.zip