
Actually the list of violations is quite large, and you can report Google Adsense violation if the website contains: adult content, hacking/cracking content, promotions for drugs, gambling or casino-related content, violent/racial content, promotions for weapons, alcohol, tobacco and tobacco-related products. What's even more interesting is that if you consider (and can prove) the website in cause uses content that is copyrighted you can report it too
Finally, if the site specifically encourages users to click on the ads, places misleading images near ads, it's difficult to distinguish the ads from the content or that if it contains any form of spyware/malware, you can report it too.
The contact form to report the Adsense violation is here: Report a Policy Violation