Since my last batch of cards (see them here) I haven't stopped thinking about crochet and cards. I had a pack of cards + envelopes that I bought at the "deal aisle" at Michael's for $2 and just thought they would be perfect for this project.
I cut a piece from the bottom (front) of the card.
Then I punched holes, I just eyeballed it, but tried to make sure they were evenly spaced.
Then with a 3.5mm hook and worsted weight wool yarn, I started to crochet.
I first crocheted through the loops to make the base, with 2 single crochets between each hole punched on the card, then I turned and made a row of single crochet and turned again and made half double crochet shells.