This isn’t something most people look into but a company called spranq in has created this font which saves ~20% of your ink. They recommend a laser printer for best results but, since I don’t have one, I tried it on my regular inkjet and didn’t find any degradation of quality upto 14pt at least. However, on screen as you can see in the attached image, it starts to get irritating. Ecofont is free although the developers do take donations.

Get it from :: Ecofont

Compariing Ecofont with Arial and Verdana