One of the fun activities that we had the kids do for our Summer Olympics was to have them each represent a country and a few day before the opening ceremony they made their own little flags. You can download the templates here, and they can colour in their flag and the Olympic rings. Then cut in half and stick to a straw.
These were a hit at the Opening Ceremony: as we announced each country the kids got to wave them crazy, and they made for fun decorations too.
IN GOOD COMPANY
GOOD ON PAPER - Free Downloads
Olympic Flags Colour In Pages
Summer Olympics Party Series