I really like the idea of fusing plastic bags together and creating a shopping bag from that. Etsy Labs has a great tutorial on how to prep and fuse the plastic bags. I used 8 layers of white plastic sheets (from the back of the plastic back). Then I cut out flowers from a red plastic bag and stuck them under the first layer. I didn't have a pattern for the bag, but there are tons out there. Finally, I used some woven ribbon that I saved from a package. I'm happy with the end result and think I'll try making some more that are even more creative. It would also be good material where you need some waterproofing...like in a beach bag.
Check out these crafts, all made from plastic bags. My favorite is the 50's Style Dress! Another good tutorial for making a really cute fused shopping bag is the Extreme Plastic Bag Makeover.
Now if reusing plastic bags isn't your thing, try making a reusable shopping bag out of a t-shirt. I saw this bag on Martha Stewart last year and thought it was a great idea!