There are a few options I suppose.

- Google doc - hacker pad - Evernote

If you would like to consider an alternative, I run a site called Postatic (http://postatic.com).

It's a site that let you create online communities (think of it as 'creating your own hackernews'

But you can also make it 'private' so that only invited and approved people can access the site, which makes it ideal for your situation. It might not be 100% perfect for your purpose but would love to have you check it out if you have some time. Happy to answer any questions!