When you are starting a new company, its often hard or impossible pay everyone for services they can provide. Some people may be willing to work with\help you build your dream in exchange for equity in the company rather than for money.
Unfortunately I do not know of any website that facilitates this sort of employment. Craigslist comes to mind immediately but I feel that if you are on Craigslist looking for work, chances are that you are also looking for money.
Are there any websites out there that do this? Anyone want to start one? :)
What you're looking for is a co-founder. Finding co-founders is hard... you have to get them to believe in your vision and believe that it's worth something, then you have to both come to believe that you are personally compatible enough to undertake a long and difficult journey together, undergoing many obstacles and problems. Essentially, it's almost as hard as finding a spouse. An equity-version of Craigslist isn't going to work because nobody wants to "work for equity"... they might be willing to join a cause that they believe in, in which case, of course they will be paid in equity, but they really have to believe the equity is worth something.