Recently, tri-fold shutter cards have been all the rage. It is a basic scoring/folding technique that is then embellished into a lovely card. It all folds up and can be mailed in an ordinary envelope.
This is my first (and only) attempt at making a tri-fold shutter card. I found it very easy to make.
This is a better photo of the entire card. Even when stretched out like this, it still stands up. The stamped images are from Oxford Impressions.
Try making one of these if you haven't already. They are a lot of fun, and make a great impact when received.