Aks HN: Looking for a simple group brainstorming web app

Hi HN. At my company we want to take a serious look at how we develop our websites and start some sort of discussion/brainstorming between our developers for improvement. It's a bit inconvenient to do this just over e-mail so I was thinking about installing some kind of web app on one of our internal servers. Something aimed at gathering opinions and ideas and allowing for discussions.

Any ideas what application would be suitable for this? I;m looking for something simple and forum-like, but where the top post/content could be edit bu anyone in order to refine ideas and summarize the discussion. It would also be nice to rank/vote on ideas. Something like a simple variant of Dell's Ideastorm or Ubuntu's Brainstorm. Any good tips for applications like that?

Thanks in advance!