Have a printer and tired of changing ink cartridges and high printing costs?
Here is a study of some text fonts by Matt Robinson which shows a comparison of several commonly used fonts and their ink usage.
The maximum the ink in a pen, the less ink is consumed by that font. Hence, 'Garamond' uses least ink while 'Impact' uses most.

There is also a font which has been specially designed to save ink.
It is called Ecofont and can be downloaded from the given site for Windows Vista, Windows XP and Mac OS X.

How Ecofont works:
1 ) You install Ecofont with a couple of mouse clicks, after which an additional button appears in the Microsoft Word menu bar with the Ecofont logo leaf.
2 ) You type in the easily legible screen font and, as soon as you click on the Ecofont print button, you print out in this font, but with little holes. The saving is a fact – with no detrimental effect on legibility or layout.
3 ) In order to optimise the legibility of the printed text, Ecoprint range has been set. Only text up to a particular point size – generally 11 points - is printed in the Ecofont font. Larger text is printed in the normal font.
After all, we all care for our planet and if we all start contributing our bit, we can definately make it a more greener planet.