Good for ages 10 and up.
Get the instructions here:
http://go.tipjunkie.com/kd/703/www.oneshetwoshe.com/2010/05/balloon-flip-flops-she-roberta.html
Dylan and alexandria makes a version as well.
Get the instructions here:
http://dylanandalexandria.blogspot.com/2012/05/easy-balloon-flip-flops-tutorial.html