I made this ribbon tutu out of organza ribbon. That is what I had on hand this summer when we were getting ready for our family pictures. The 3 yr old wanted EVERYONE to be butterflies for halloween and so I knew that I would just use what I already had for her costume.
I used the same method as the no sew tulle tutus. Some instructions can be found here on Ehow for the ribbon tutu (I did not use these instructions but its the same way that I did it).
On a side note I would definitely use heat seal or something else to seal the ends of the ribbon. I did not and the whole day I kept pulling off strings.