Ok, sure. I do realize that it would be much easier to go to staples, the drugstore or the stationery store and just buy an envelope. But how much fun would it be to try to fold your own? I'm here to report that the answer to this quandry is: A LOT OF FUN.
This is a great website with (mostly) dummy proof instructions on how to fold all sorts of envelopes. For a paper lover like me, this is sort of akin to web crack, so beware.