In this video I show the effectiveness of a mini laptop fan on the Raspberry PI coupled with a heat sink.
The fan I used was a GM0501 PFB 3-8. The idea to use this fan came from
http://ultimateohm.blogspot.co.uk/2012/08/mini-fan-for-raspberry-pi.html
The diagram of the GPIO layout I show on my screen is from
http://www.youtube.com/watch?v=q_NvDTZIaS4
The link can be found in the description at the bottom