Lots of envelopes have patterns printed on the inside, usually in blue (although if you are with a certain phone company you may be lucky enough to get orange ones) and these make great craft papers. I keep a selection of pretty and undamaged ones in my craft stash.
I've put together a card using the papers from just two envelopes. I stamped and embossed flowers on one inside paper, then cut them out
The second piece I cut into rectangles and folded each in half, then cut a half-leaf shape with the central vein of the leaf on the fold. Holding it at an angle, I pit the still-folded leaf through a corrugator. When opened out it produces a lovely stylised leaf.
Finally I assembled a selection of leaf and flower shapes to create my card.