One of the advantages of being a university student is that there are ample opportunities to be a psychology experiment test subject. If you’re ever bored and could do with a bit of cash, it’s well worth checking out if there are any psychology researchers looking for test subjects. Usually you’ll end up sitting in front of a computer for about an hour pressing buttons in response to stimuli, and you’ll get something from £5 to £10 in return for your troubles.
I find it particularly interesting because the researchers will often try to explain the rationale behind the experiment to you, and you’ll invariably find out some interesting cutting-edge insights. The researchers are always very grateful to have test subjects (despite the fact that they’re paying you) and the warm glow of just having contributed towards the progress of science and our understanding of the universe tends to mitigate any feelings of guilt that you might have about dozing off during the experiment (not that I would ever have done such a thing, of course).