These are the directions for fabric postcards, I'm sure you can adapt them for a card:

http://www.clotildessewingsavvy.com/freepatterns/pdfs/jan06_heartfeltgreet.pdf

There's no way I would just pop one of those into a mailbox after all that work. Definitely an envelope for me!!
Now I might have to try to create a fabric greeting card, though.The postcards took really nice.

This is not a complete fabric idea...but I'll tell you what I have done once.

I used a heavy card stock in a tanish color.

Cut and folded it.

Cut a good size heart shape out of the front of it.

On the back side of the heart I used old quilt fabric and sewed it to the card with the quilt facing the front. I used a fancy stitch that looked like quilt stitching and followed around the edge of the heart. Stuffed a little stuffing to make the heart puff out a little and then cut a backing for the back side of the front of the card. to cover where the back side of the old quilt was. Glued that on and had a card.

It has been a long time ago that I made those but I think at that time I sold them for $2.00 each.

patti

There are instructions for very modern, very hip ones in "Denyse Schmidt Quilts: 30 Colorful Quilt and Patchwork Projects." Not sure if these are what you want, but I sure love them!

Here is a link that might be useful: This book's listing on Amazon