Create Web Application to Allow Users to Crowdsource Ideas

Looking to have a site built from scratch that will allow users to create a profile, enter an idea, and pledge a certain amount of money to this idea. Other users can then view all ideas and pledge money to various ideas that they agree with. Once an idea hits a threshold set by the originator, it is then fully funded and queued for building. Need many funding options such as the ability for users to fund via paypal, google checkout, direct cc billing, etc. Need many sorting and filtering capabilities, such as the ability to show on the home page the closest idea to being fully funded, the highest rated idea, the user with the most funded ideas, etc. Need many twitter and facebook integration capabilities, such as the ability for the originator to tag people in his idea, and as the idea progresses, messages are sent to those people that have been tagged stating it's progress, and eventually it's state of fully funded.