I have also finished a hat myself: the Ruche Beret desigend by Susan B. Anderson. I just love this design.
I chose an alpaca/silk blend yarn for my hat because I didn't want it to be too scratchy. Other people involved in the chemo cap project are knitting hats in cotton or acrylic.
This hat took just a little over one ball of the yarn that I was using, and I have enough left over to try another style of hat to donate.
If you'd like more details about this particular hat, including the yarn I used or where I found the pattern, please visit my Ravelry page.
If you are interested in donating a hat to the chemo cap project, there is still time - the deadline is March 7. It's a good chance to have fun and help out - plus, for each hat you donate I'll enter your name into a drawing for a $20 gift certificate in my Etsy shop!