What groups should we have?
Groups are managed by the Organic Groups module. A group is simply a node which can have other nodes (articles, links, pics, etc..) associated with them. Groups can be private or public. Content created within a group can be public or private as well. Groups have members who can contribute content to the group. The group node can be customized to be a home page for the group.
As a member, you can create a group. Like articles, when you save the group you created, it will be reviewed before it can be published.
I currently have two groups available to the public. They are Developers and Themers. I think that these groups are too broad in nature and could be segmented into a more granular set of groups.
Please list the groups that you think would be beneficial to a site like this. It is a great way to associate different types of content with a common theme. Groups can (and probably should) be different than the categories (terms) set up in the taxonomies for this site.

Already in place:
Developers
Themers
Suggestion:
Webadmins - For those members that don't necessarily belong to Developers or Themers but still manage a site. They may have payed someone to install the site for them, and now perhaps they are a little lost in how to continue to manage the zillion parameters that makes their site up and running.
SEO - Yes, you got it. For specialists on search engine optimization.
Security - To make sure your site is secure is importent and the topic area is kinda huge. So I think those that specialize in this should have a group.
Hardware - because without it we are all lost.
OS - Operating systems.
Webservers - not the servers, but the webservers Apache and IIS and whatever else is out there.
Webhosting - good hosts, bad hosts, hosting your own server and why being a webhost is such a bad idea unless you hang around with nothing to do 24/7 and are loaded with money.