No need for a hole, just use a tagger, their needle goes right through the card stock. I had my tags made by
www.Vistaprint.com, I arranged the text vertically and they came out awesome. Cost was 250 for slow shipping rate of $4.21!
I bought a very inexpensive tagger for like $14.95, plus a couple bucks for a second needle (which I am already using now, so buy a full pack of them)
Here's a URL that shows what these taggers look like:
Innovative Label: Clothing Taggers / Accessories:0