<p><a href="http://www.nasa.gov/mission_pages/station/research/experiments/1115.html">This article</a> states that 3D printing has been accomplished in outer space, on the International Space Station.</p>

<p>I'm curious as to how this works differently from 3D printing on Earth. Are there any extra measures that needed to be taken to ensure that the filament would be correctly extruded onto the print bed, or during other steps?</p>

Most likely, the 3D-printers used on ISS does not incorporate some fundamental difference that allow them to print in zero gravity.
Some people over at
3Dprint.com
raised a very similar question, and figured that when turning their 3D-printer upside down and on it's side:
there’s not really much difference at all. It’s quite interesting to see how the orientation has little effect on the quality.
One of the early 3D-printer models - the
Bukito
printer - demonstrated that their printer was so portable it even could print on the move, and
upside down
.
In other words, some consumer 3D printers already print upside down, and so they would probably print in zero gravity as well!
(That's the short story anyway. Have a look at Ryan's post, who gives a great description of the more intricate parts of space printing!)