Well I wrote out some instructions, and hopefully if you click on the picture you will be able to see them. If you then right click you should be able to save them.
I used strips of 20 cm by 10 cm (8" x 4") but you could use any size you wanted. Basically you need two pieces of card the same size. One cut in half horizontally and one cut in half vertically. They are then scored at the 1/4 and 3/4 mark of the long side (a bit like a gatefold card).
You lay the two horizontal pieces one below the other. Put some glue in each of the four outer corners, and then attach the other two pieces that have been cut vertically to the corners. Then just keep folding and creasing. The front layer will open like a gatefold card, the next layer will open from top to bottom, and then the last two will repeat this sequence, until you get back to the beginning.
(bit difficult to explain - but do have a play. The result is quite fascinating.)
Have a look at Fiona's never-ending snowman card on: here It is brilliant.