Wren - Offset your carbon footprint by saving rainforests
EcoCart.io - Free e-commerce plugin for merchants to offer carbon neutral orders to their customers.
Capture - A great free screen capture utility that allows you to capture either a window or the desktop and save it to either a file or the clipboard.
Klima - Go carbon neutral
Treepoints - Fight climate change and earn rewards
Treeapp - Plant a tree for free, every day, in less than a minute