Part of this is a repost from last year that we thought would be timely considering all the Christmas cards we’ve been posting:
"With all the Christmas card posts we’ve been putting up (i.e. Christmas Card a Day) you’ll most likely need to craft some handmade envelopes to go along with any creations you’ve made. Here are some free downloadable envelope patterns to give you a start. Some are standard looking envelopes and others you’ll see are very unique!
Martha Stewart has a template for making business card envelopes. The ones in the link are made from leather, but you could also make them from felt or paper. (Also, check out this link for making custom envelopes. One photo is shown at left.)