Here are various tips for using and reusing envelopes.
I save junk mail envelopes. Cross out the pre-addressed side well and mail bills, personal mail, or send field trip money to school, sort photos etc. - Submitted by Fly
Ask the greeting card lady at the supermarket if she has extra envelopes. I get all the free envelopes I can use this way, and sometimes free greeting cards, too. She throws away thousands of envelopes every year. - Submitted by Heidi
I always save envelopes that come with solicitations that we don't donate to, or ones that come with bills that are auto-deducted, and use them for mailing checks to places that don't provide envelopes, or for mailing letters to friends and family. If the self-addressed writing on the envelope needs to be covered, I either glue pieces of paper (cut out from the backs of scrap papers whose fronts have been printed on) over the print, or I use the white unused parts of blank Avery labels (I make our own unique return address labels). - Submitted by Debbie