I'm actually playing around with business cards in wood right now. I haven't tried very hard though. I first tried hardboard and found that to be too fibrous for a rotary tool. I recently tried some wood and I love the results. I had a piece of quarter sawn white oak laying around and threw it on the CNC. The tool did a great job, however, there are too many cells in the wood. I'm thinking about going with something a little bit more hard/waxy...also I might try spray painting the wood, machine it, then sand off the spray paint. Here are some quick pictures of my test: