Just found this logic gate simulator. Make use of switchs, bulbs and wires and connect them with items from the toolbox on left for some fun! There's help available at top right side. Link: http://joshblog.net/projects/logic-gate-simulator/Logicly.html Have fun. : ))
A very nice online live logic gate simulator here which is very easy and fully free ! you can save your circuit for next time use and show it to another people http://www.electrosight.com/logic-gate-simulator