Mac OS X: PDFs are great, but constantly printing out endless amounts of documents wastes a heck of a lot of paper. The World Wildlife Federation has created their own PDF format that is unprintable in an effort to end that.
Right now, the file format is only savable and readable on Macs, but a Windows version is coming soon. The software is a plugin that allows you to save anything as a WWF file from the print menu in Mac OS X. It's basically the exact same thing as a PDF, except you can't print it out. It also adds a small explainer to the bottom of each WWF document. Download here. Source lifehacker.