I have just signed up for the Guardian's n0tice (the 0 is a zero) - it's free. It's a community noticeboard for news and events and I saw it demonstrated by the Guardian's Sarah Hartley @foodiesarah at the MediaFabric event in Prague last week.
First impressions are that it could be useful. It allows readers to rate articles and say whether they are important or trivial etc. My first post was extremely trivial. I've added a few events, too.
At I write (27 Oct 2011) it's beta invite only - but mine arrived really fast. Give it a try.