When I wanted to make wine cork trivets for a library program, a friend gave me a huge box of wine corks. I had plenty for everyone in the program (read about it get a PDF tutorial from the link above) and plenty more to make trivets for friends and still more left over. I started to make a square trivet when I decided to keep going to make a cork floor mat for my bathroom.
It is big enough for me to step out of the tub and onto. I’m not sure how long it will last, but since it only took a couple Monday nights of watching The Voice and using a hot glue gun to piece it together, I’m not too worried if it only lasts a year to 18 months.