iImage Information

Never buy an envelope again! Wow your friends and bill collectors with mail in these envelopes you've made out of junk. This envelope looks like the sort you'd purchase, with angled bits in the back. Check it out, try it, make someone happy & reduce the landfill all in one fell swoop. And please remember to rate my Instructable. Thanks!
Step 1Materials Collection
iImage Information

Sources for free and fabulous "junk" paper are everywhere: junk mail, NYT Magazine, gorgeous catalogs for things you can't afford, old calendars, discarded books. Begin collecting as soon as you can because packrat-ism is a positive thing in this case! Whatever you don't use can come in handy for collages and other projects.
Here you see an excellent source for gathering raw materials. For envelopes, you'll want paper at least 8-1/2 x 11", and bigger is better. You will also need scissors and scotch tape. In the final step, you will want a Sharpie pen, or white paper to tape onto your envelope, for addressing purposes.
i would remind folks though, that the US postal service has requirements for envelopes and postcards, including maximums and minimums for length, width, and thickness. so for instance using thin paper, like thin magazine, bible, or phone book pages, generally doesn't make an envelope thick enough to avoid getting chewed up by the USPS machines. i generally only use magazine pages if i'm sending a letter or card that i know will give it a good, sturdy thickness and survive the machines. i once had an envelope returned by USPS because the corners weren't perfect right angles, so keep this in mind!
check this USPS link to be sure: http://www.usps.com/send/preparemailandpackages/measuringtips.htm
I currently live in México, and to date, my envelopes have travelled well internationally. cheers to up-cycling!