I like using business cards too, but did run into problems when I made longer earrings. I didn't like when they hung off the edge of the card.
Now I use large oversized postcards from Vistaprint. I created a neutral background and can cut 4 cards that are 2" wide and 5.5" tall from each postcard. (My mailroom at work can cut them really fast for me.) So with 100 postcards, I can get 400 earring cards. And if I don't need them that tall, I cut them off. I've used leftover pieces to put bobby pins or hair barrettes on.
As for punching holes, I can do several at a time. I put cork board underneath and punch the holes with a simple thumb tack. The hole works for me… I don't like them too big or too tight.
I don't even try to make my holes in line. I purposefully punch them one higher than the other, by at least a 1/2 inch. I think the earrings just look artsy hanging that way, and well, you really can't mess them up.
Here's the only example i could find handy on this computer...
I can also fold these cards in half like a tent, and have them sit up on the table. And if I want to hang them, I have bought the self-adhesive backs that you just peel and stick on. I cut those in half too, to get twice as many, and they still work great.
Here they are:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
That's just my 2 cents worth on earring cards. I love seeing what everyone does for displays... some really great ideas all around!