Is there any platform where we can find developer/designer or where designer and developers collaborate and contribute. There are lot of website where this things happens but they are much like a bulletin board, what I am looking for is a platform which can ease in discovering developers designers who are willing to collaborate. I don't want to find a cofounder, or a lead, I just want to collect bunch of people and start working on the idea just like you do in a hackathon.
Getting Started Development Design
Drupal, .NET, Ruby - all kinds of hangouts for different groups of people making cool things everyday.
Check collaborators on successful github.com projects. There are lots of linkedin.com groups too
This may be what you are looking for...
The only thing that sounds similar to this that I am aware of is startupweekend. I think the team that helps you gets a cut of the equity though if you are able to build a business.
Assuming nothing like this exists, sounds like a good online social business idea.