I was browsing through this library book last weekend and got inspired. I made a French press cozy out of 2 pieces of a felted sweater.
It was fun sewing therapy, even though the cozy looks decidedly homemade. But it does really keep the coffee warmer longer.
I still haven't made a cozy for my teapot, although sometimes I design it in my head as I'm falling asleep at night. Oh, the lovely possibilities!