I just published a post about the two different types of inbound networking groups. I am forming one that is like the second type: Businesses that sell the same thing, but don't really compete.
I plan to launch a group that only inbound marketing agencies can join. The goal will be to create an international organization of inbound marketing agencies that work together to promote the concept of inbound marketing and inbound networking by helping each other generate more visibility for each other's content.
As HubSpot has built the inbound marketing movement together with our agency partners, I've been amazed at how collaborative our partners have been; how willing they are to share advice; how often they share each other's content with their own audiences; how often they outsource business to each other. They occasionally compete to win clients, as many of them work beyond their geographic territory and have a fairly broad service offering. But, they still work closely together to help each other. For example, PR 20/20 wrote a book about how they built their agency. I just got a sneak peak of Kuno Creative's secrets to success, which they'll share at Inbound 2012. The agencies that help their peers, find that they gain much more when they give.
I will personally lead this inbound networking group. There will be a small fee of $100/mo. I will use the fee to hire an editor, a chief content officer of sorts. The editor will coordinate the editorial calendar, manage submissions, edit articles and coordinate social media promotion of the content by the members. I will probably invite HubSpot's Gold and Silver partners as the first members. I will also invite anyone who gets an inbound networking group going and gets several members to join their group.