Easiest way to generate traffic for student optimizers

I'm teaching a class that involves multivariate testing and analytics. Ideally, my students will be able to setup their own tests and see the results... inevitably, the hardest thing for the students to do is to generate the traffic to see any results for the test. The best students usually top out around 50 clicks.

What would be the best way to help them generate adequate traffic, short of buying it or appealing to various social networks? Are there any site topics that are near-guaranteed traffic generators?