
Here's another fun website where you can have some fun and learn, and at the same time do some good. Similar to the Free Rice website, this one is a general knowledge quiz which donates a leaf for each correct answer. 15 leaves make a branch and 20 branches make a tree.
The website is called Answer4Earth and currently splits its donations between two non-profit charities, Trees For the Future and The Fruit Tree Planting Foundation.
Have fun. Earth Day 2008 is on April 22: this would be a great way to do something for our planet.