Depending on the size of the paper you use, this origami card holder can hold either business cards or credit cards prety nicely. It is a simple yet very practical origami. Find out how to fold the origami card holder here.
This is another possibility for my 'smart' concept. These suits are not quite as well put together as the other origami suits but I could adapt these easier to accommodate my portfolio and business card on the inside of the jacket.