This is pretty cool from one of my favorite follows on Twitter, Entrepreneur.   

Culture is a popular topic often misunderstood in the business world. It’s not one-size-fits-all, nor is it easy to describe exactly what separates a great culture from a poor one. Perhaps the simplest way to determine culture is the “temp worker test.”
Because  temps are only there short-term, they can offer a clearer, unbiased perspective on what it’s like to work at your company. Were they treated with acceptance, kindness and willingness to help out? Do they want to work there fulltime, if possible? Or can they not wait to move on to another company? Their experiences may not be the end-all, be-all when it comes to your culture, but it’s a good indicator.