Article directories are known to give incredible link juice when used correctly.

I run an article directory, and I've had a few hundred emails from members saying how I've helped them get to PR2 in a few months!

Article directories give great backlinks because users are constantly looking for new information. With Google getting 1 billion searches a day, it's understandable why you would want your article to be found, you link to be clicked, and then your ad to be clicked...