If you're looking for developers, you can try outsourcing sites like oDesk, Freelancer, Elance and Scriptlance. Considering the popularity of facebook today, I'm sure there are a lot of facebook developers who are willing to do freelance jobs.
Reviews of the outsourcing sites mentioned above can be found in this article: http://www.timedoctor.com/blog/2011/02/ ... o-use-them
The short reviews will give you an idea of what the site is and how they operate. You can also read in the article about how you post jobs in the sites. There are actually a few guidelines when posting like including all the details as well as the requirements.
There are also guidelines that you can read in the article like checking the profile page of every service provider who bids on your posted project/job (you can post them in sites) so you will see their rating and feedback - these will indicate their performance in their previous work.