I love to read other blogs for inspiration, and earlier this year Carmenesque had a blogpost about packaging and recyling.
It reminded me of my own envelopes, that I have made since I was a full time student. Being a full time student, money were sometimes scarce at the end of the month, and it could mean that you would rather save money than spend it on new envelopes ... You simply took what you had at hand to make new envelopes, and you could often find cool papers in magazines, brochures etc. Later on I bought a plastic template at the local hobby store so I did not have to used the miserable envelope that had served the last of its life as a template.
I still make my own envelopes - and I still write letters. I use email everyday at my job and find it relaxing to writing to friends and family the old fashioned way - email is only used if I want a quick answer.
A while ago I read somewhere, that envelopes was a scarce commodity a few hundred years ago, so an "envelope" was often reused 2-3 times, even more in some cases. I do not reuse envelopes, I recycle them instead in the papercontainer situated in my building (but only the letters that aren't "keepsakes").
All you need is cool pictures etc from magazines, glue or double adhesive tape and scissors... and if you do not have a template, I am sure that you have an old evelope, that you can use as a template.