When you receive a large envelope in the mail made from Tyvek, the strong synthetic polyethelyene fibers, don't toss it in the trash. Because Tyvek envelopes are water-resistant and nearly impossible to tear (but can be easily opened with scissors), there are myriad ways to reuse them. One idea is to reuse the envelopes to store important documents, photos and other sensitive printed pieces. The water resistance will protect them, and the natural UV light barrier of the material will prevent fading. Just seal it with packing tape to make sure the Tyvek protects your precious documents. You can write what's in the envelope on the outside with a permanent marker.