There is a window film at Home Depot called Artscapes (you can get them at the store or their online site). They have about 6 styles and all you do is cut them to the size you want them - wet the window and place them on. You can move them while the window is still wet and once you get them placed nicely, you squeegie them on.

I have them on a couple of my windows where I don't want to use curtains. They look very nice and prevent anyone from seeing out or in, but they do let light in.

If you want to check them out just go to the Home Depot Website and type in artscape in the search window.