Off-the-shelf social networks are now available to create a home for your interest area or organization, whether you write a blog, run a Yahoo group, or have a real world group.

LinkedIn Groups is a limited way to promote your group and far from a platform for group interaction, so it's just a part of your group toolkit, just like a blog, wiki, email list, etc.

There are a variety of choices - free (many of them) vs. fee, hosted vs. proprietary software vs. open source software, etc.

Links of reviews and services:

Review - 9 Ways to Build Your Own Social Network

http://www.techcrunch.com/2007/07/24/9-ways-to-build-your-own-social-network/

List of White Label (Applications you can Rebrand) Social Networking Platforms - over 50 included

http://www.web-strategist.com/blog/2007/02/12/list-of-white-label-social-networking-platforms/

Greg Acuna LinkedIn question - What is the best software package for creating and hosting a Social Networking Website?

http://www.linkedin.com/answers/technology/web-development/TCH_WDD/73544-3269664