A good solution to the quest of this session would be a platform where people could not only fund anyone's ideas but help to realize them in any way they can.
If it's a rather simple idea, like building something, people from the local area could offer to supply building materials (from what they have in their sheds and don't use anyway, for example) or offer help in building it. That way they could be the part of the process themselves, meet people and make friends.
Ideas could range from small and simple personal aims to grandiose ones, like the colonization of Mars. There are many ways in which people can help, not only money. Someone (who's proficient in that field) could offer to write a marketing strategy for a specific product/website, etc.; some people could offer to drive required materials or people from place to place, when necessary; someone might know people proficient in specific fields in which the project requires deep knowledge, to be realized; someone might know some investors who might be interested in that particular idea, etc, etc.
The completeness status of the idea could be shown next to it and constantly updated as things progress further. The type of resources/help that is most needed at a particular time would also be emphasized. Ideas that are nearing completion might attract support more easily.
The first step would be for the author to describe the idea as detailed as possible. The next step - to make a draft of all the steps and resources required to complete the idea. The second step could be done either by the author or collaboratively with users of the platform who became interested and willing to help.
Once the draft would be done, people could start offering their help for various required steps and resources. Crowdfunding could be the base model for financial support. When the idea becomes realized all the contributors would then be invited to participate in an official event or opening (if that's feasible), get small symbolic gifts, discounts on the product, free samples, or be rewarded in any other way. For example, in the case of Mars colonization, the most influential contributors could be amongst the first travelers to the planet.
The part of this where things get a bit complicated, I think, is the rights to the idea and especially the final product/creation. If the final product is a result of everyone's collaborative work and resources, can the author of the idea own rights to it in the end, just because it was his/her idea?
It would be rather easy for ideas directed towards common benefit without any wish for personal profit, e.g. solving the traffic problem in a particular city, just for the sake of more peaceful life of its inhabitants. Maybe the platform could be primarily dedicated for open-source, non-profit ideas. But even in that case, the author would want the idea to turn out according to his/her vision, so the sense of ownership would be present to a certain extent.
However, this is not a major drawback and could be worked out with a set of predefined rules/standards.