What immediately comes to my mind is Justin.tv. It was originally just a website featuring one guy constantly livestreaming his life via a camera on his hat. Eventually it became a livestreaming platform and gave birth to what's now Twitch.
I've read a few comments in this thread to the effect of "develop a personal brand," and I think that's exactly what you need to do. Firmly establish yourself as a high-quality, in-demand freelancer, and then transition towards forming a network of freelancers. Maybe initially it'll only be people you've directly worked with whose quality you can personally vouch for. Once you show you can provide quality talent and have drawn in clients, then you can start opening up your platform to more freelancers.
I'll note that I don't have much entrepreneurial experience, so take my advice with a grain of salt.