Here's a good place to find controversial topics and content in just about ANY niche:
Writing on a hotly debated and controversial topic can get your article more hits, as interested people will be more likely to share your article with their friends.
Or, you can use the site to get ideas for controversial headline ideas.
Make sure you have a Facebook and Twitter share button on your site to make it easy for readers to share your article.
One last thing - writing on a controversial subject doesn't mean you have to take sides in a particular argument or have an extreme viewpoint one way or another. You can just write from a neutral position and list the pros and cons, different arguments etc. Leave it up to the reader to make up his mind which way he / she believes, if you can. Taking a particular stance on a controversial topic like, for example, abortion, can potentially alienate you a little from some of your readers.
Or you can just be controversial yourself... Whatever floats your boat