Cliff's class.

These cards seem to be very popular at the moment.

I made one earlier this year for my fiend Alun's 50th birthday.

They are called Tri shutter cards.

There are a few variations but here is a link to one I first made.

http://craftiblog.wordpress.com/2009/04/23/2009-04-23-quad-fold-card-sample-tutorial/