The solar eclipse of May 20th 2012 created some very artsy crescents when viewed through filtering leaf shadows.
I was not in a good location to see the eclipse, with gigantic mountains rising steeply upward and the sun just about to go behind them, but when I saw the pretty crescents, I quickly grabbed my camera and zipped around town, looking for buildings that had nice crescents cast upon them.
I have no idea what viewing the sun directly does to the eyes, but upon talking with a couple friends, it seems they had done so and when I called them about 10 minutes after they gazed directly at the sun, they still were having vision troubles.
Curious, I did an internet search to find out if there truly is a reason to not view the sun during an eclipse. Apparently there is. One does not want to look at the sun unless it is entirely blocked. An interesting article on the topic can be found here and another article here.