It’s difficult to provide live examples of SEO spam techniques. If you reference a site which you don’t control, your live examples may disappear without warning – and the internet will be that much better because of it. If you host them on your own server, you run some risk of being tagged because of it. Google’s filters for spam techniques appear to be human controlled, at least to some degree, so I’m bound to hope that they’d notice that your site is posting examples, rather than making use of the techniques.

For now, I’m going to refer you to the latest post from Matt Cutts, in which he refers to a number of past posts in which he outlined "concrete examples of violations"
of the Google webmaster guidelines.