We've discussed similar products like this before, but these firefly jars are so extremely easy to make! I'm not entirely sure how much light they actually emit, but this would be such a cool alternative to patio lights.
All you have to do is find some mason jars, and flick some glow-in-the-dark paint in the jars, let them charge in the sun during the day, and voila! Glowing lanterns at night.
I did some research and apparently there are some non-toxic glow-in-the-dark paints out there. I would hope that they have a fairly low environmental impact as well.
Related Post: Set the Mood: Our Favorite Outdoor Lights Under $100
(image: We Heart It)