If you need some good content for Adsense niche sites, I suggest trying Text Broker. They are easy to work with, have decent writers, and are inexpensive for adsense site content. No, it is not content I would use for my main websites, but it is fine for your second tier sites. The writers understand SEO and follow your optimization instructions well for each article. The finish the article orders in usually 3 or 4 days and the archive at text broker is easy to navigate your finished articles.