What google doesn't want to be a part of
From https://www.google.com/adsense/support/bin/answer.py?answer=48182.
Violent content, racial intolerance, or advocacy against any individual, group, or organization
Pornography, adult, or mature content
Hacking/cracking content
Illicit drugs and drug paraphernalia
Excessive profanity
Gambling or casino-related content
Content regarding programs which compensate users for clicking on ads or offers, performing searches, surfing websites, or reading emails
Excessive, repetitive, or irrelevant keywords in the content or code of web pages
Deceptive or manipulative content or construction to improve your site's search engine ranking, e.g., your site's PageRank
Sales or promotion of weapons or ammunition (e.g., firearms, fighting knives, stun guns)
Sales or promotion of beer or hard alcohol
Sales or promotion of tobacco or tobacco-related products
Sales or promotion of prescription drugs
Sales or promotion of products that are replicas or imitations of designer goods
Sales or distribution of term papers or student essays
Any other content that is illegal, promotes illegal activity, or infringes on the legal rights of others