I picked up a couple FedEx envelopes (large and small sizes). They are made from Tyvek, and of course I had the idea to make a stuff sack from them.
I just got them this morning. After getting home I did a quick search and found this video: http://www.youtube.com/watch?v=IyYuET-UOEk. Of course, it really is hard to have a truly original idea these days. I'm thinking I'll have a go at it with some adhesive or Tyvek tape instead of the needle & floss as in the video.
I just thought I'd share the idea and collect other's thoughts.