I use requester dot mturk.com/mturk/welcome - the service is free just define the type and size of content and what you'll pay - I pay from $3to$5 USD per article.
Here is one of my typical requests:
Write an original article about collecting American “Western Antiques” the article must be original and at least 400 words in length in addition to a 100 word summary of the article. The main focus of the article should be to reveal useful knowledge, ideas and practical tips which readers can use. You should include links to between four to six complementary (similar) websites. Use correct English grammar and spelling. Please do not waste my time and yours with articles that you “cut and paste” from the Internet, I want ONLY original articles. MUST have both the ARTICLE (400+ words) and the SUMMARY OF THE ARTICLE (another 100+ words) in order to be accepted. The purpose of this article is to provide useful information to readers, not to promote a particular product, service, program, company or website. You must also agree that you have been employed as a ghost writer to write it exclusively for me, and for which I alone become the 'author' of the article.
I would expect to have an acceptable article within two to three hours of making a request like this.