Dell's IdeaStorm is a community where you can post ideas, comment to them, promote & demote them (voting system). The best voted ideas bubble up and so the voting system determines the following order of appearance of the ideas. It is powered by "SalesForce Ideas", a system I can't pay for in a lifetime.
I have tried to build a comparable system, based on wordpress and some plugins, but it is more complicated than I estimated.
Do you have any suggestions?