Just check out this little gem called Ecofont.
It has small spaces removed from the inside of the font, but not so much that it affects legibility at normal book sizes. AND its a derivative of Helvetica. Its ends up using 20% less ink than its full-bodied counterpart and best of all, its free to use and share… What's more sustainable than simply using less ink? This is truly an amazing idea and I'm happy to share it with you. Guest post by PSU-GD grad Nic Pederson. THANKS NIC!