http://www.mathgames.com/skill/6.46-multiply-and-divide-decimals-by-powers-of-ten (whole numbers and decimals)
http://kids.britannica.com/lm/games/GM_5_5/GM_5_5.htm
http://www.snappymaths.com/multiplication/multby10or100/interactive/multby10imm/multby10imm.htm