Liberation Mono is styled closer to Liberation Sans than Monotype's Courier New, though its metrics match with Courier New. The Liberation fonts are intended as free, open-source replacements of the aforementioned closed source fonts.
Although similar to the popular Deja Vu monospace font, Liberation Mono takes up much less vertical space, allowing more lines code on the screen at once.
A notable quote from a commenter:
This font is absolutely fantastic. It doesn't have as much personality as, say, Inconsolata or Consolas, but what it lacks in personality it makes up for in readability. It is also very similar as the font Cousine, available on Google Fonts, but supports a wider set of characters. My favorite features of this font are the dotted zero, perfect symbols, flush underscore, and overall transparent design. I've been using it for more than a year and highly recommend it to any programmer.
Deja Vu 12pt: http://imageshack.us/a/img543/9845/dejavu12.png
Liberation Mono 13pt: http://imageshack.us/a/img43/691/liberation13.png
Download Link: https://fedorahosted.org/liberation-fonts/