I saw this in National Geographic magazine 2 days ago and found it a bit interesting.
Take a look at this font below

You probably noticed the holes in the letters, if you print this out you will save ink. According to the Ecofont website you can save up to 20% of ink

After extensive testing with all kinds of shapes, the best results were achieved using small circles. After lots of late hours (and coffee) this resulted in a font that uses up to 20% less ink.

Of course you can save more by not printing at all. :-)

So I decided to play around with this, I downloaded the font (you can download the font from the download link on this page: http://www.ecofont.eu/ecofont_en.html) and typed up a page in Word 2007. Below is the result:

I increased the font size for every and also compared bold to regular. The last 2 lines have a size of 72.

So what do you think? Does this make sense? Also how much do you print on average? I really don't print that much at all, at home I don't even have a printer. As a matter of fact I haven't used a printer at home for at least 6 years or so

Will you use this font?