That site is aimed at entrepreneurs, with a particular focus on people who are bootstrapping instead of pursuing VC money. A lot of the discussion there tends to involve marketing, although the site isn't necessarily aimed at marketers per-se.
There are a lot of good entrepreneurial teams as well, but a lot of them have one time fees to join (part of a vetting process).
The one I mentioned above is free which is somewhat unusual for such an active community.