I always have a surplus of blank cards and envelopes at my disposal. The other things I used were my: bookbinding awl, embroidery floss, a cutting mat, needlepoint scissors, and a sharp needle. Once I knew what I wanted on the card I "illustrated" it by stabbing a series of tiny holes with my bookbinding awl. Then I picked out my colors and 'connected the dots.' (I used 'running' stitches for all of the cards, but there are many other methods).
Here are just a few of the latest embroidered cards:
Please keep an eye out for similar items in my etsy shop soon! :) http://www.etsy.com/shop/dessertforbreakfast