Startup Ideas Exchange / Community?

I am looking for a portal / community where people post and discuss startup ideas. Of course I know about HN, Quora etc. but there is too much noise. What I would really like should be something like:

- everyone can submit ideas, put them in categories, assign tags - others can upvote / downvote ideas - people discuss how the first steps to executing it could work - you would get immediate feedback and first beta users

Does anything like this exist?