This is Korean laver. It's roasted seaweed and it comes in thin sheets -- thinner than sushi nori. It can be used in lots of ways, but my favorite is to reconstitute it in hot water and sprinkle a little sesame seed & sesame oil in it and eat it just like you would cooked spinach.
You can also crumble it up and cook it in scrambled eggs. Or just add it to other recipes as a bright green accent with a lovely flavor. The Welsh actually use laver (a slightly different seaweed species) in bread and other dishes.
I got this at an Asian grocery store, but it's fairly common I think, and can be found online pretty easily. The flavor is subtle and wonderful, and I hear it has lots and lots of good vitamins in it.