Plant trees by surfing the web with Ecosia
This is the best browser ever! It works exactly like other search engines but the company plants trees with the money they make. On average you need about 45 searches to plant a tree.
Since I installed it on my computer a couple of months ago, I have helped Ecosia plant about 14 trees! That's about 305kg (672 pounds) of carbon dioxide per year. To put that into perspective: that's a little less than the CO2 emissions I caused flying from Indiana to New York. But it's A LOT better than nothing.