The Freelancers script allows anyone to run a professional site like only large companies could until now.
How it works is that people looking for freelance work ("providers") signup, and companies ("buyers") looking for professionals post their projects on your site. Providers bid on the projects, the buyer picks the bid he likes, and the project begins. You can take any commission you want based on the bid amount! It's a lot like an auction, but the buyer has more control over it. All you have to do is promote the service. Absolutely everything else is done by the script, even money deposits! This type of service often gets people coming back to use it several times, it has the potential to grow very quickly.
