Wren - Offset your carbon footprint by saving rainforests
Buy For Life - Find the most durable and sustainable products in the world
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.
Waste Not - Open-source database of sustainable suppliers
Treepoints - Fight climate change and earn rewards
Ethical Resources - Huge repository of ethical alternatives to mainstream stuff