Github is an excellent place to make your project visible and let others contribute (project fork) without interfering with your work. Then you can merge whenever with whoever's fork. Github has wiki pages, source browsing and activity graphs. The site is fast too.
** UPDATE **
Github may not have "find project creators" features, but will certainly make your project visible. There is no magic behind it, and this is just like marketing a product; you have to make it visible and interesting. It doesn't have to be complete, but you need to have something to show before you get "inverstors" to join in. :) Also, even if a project has more than one creator, there should only one to lead the project, otherwise the project might not follow a straight line in development. At least this is true for embryo projects.
In my comments, I have mentioned that a project that could help in what you are asking would be a site kind of like StackExchange where people start up ideas about projects, where other could join in and talk about it; discussion could be categorized in programming language, project type, etc. Ideas could be voted up and commented, etc. etc.