This is a multifaceted question.
If you have teachers in the same institution, there is no problem just setting up a private course. Across insitutions: this is another matter.
If you want to look at a good community based on Moodle, I'd suggest
http://scope.bccampus.ca/What functionality do you need for this sort of professional community? I'd suggest
- interactions and discussions
- file sharing (with detail, maybe votoing/comments) Finding the good stuff is always a problem. The remembering where it is.
- a collaborative work area. Moodle wiki? I havre mixed feelings.
- Then you need to know who is there (profiles). (I like the idea of "I'm interested in Z, Y and X, feel free to chat if you like")
Forums as standard are powerful, but still just a little primative. No drafts, only one attatchment, search is a bit clumsy. But there are many many communities that live with these very well.
There are a few challenges to this type of sharing which in my opinion have to do with a couple of missing functionalites in Moodle. One is the lack of a good file sharing functionalty. [This is one reason why people like Google Apps] You can of course add a file as an attachment to a post. But only one, in the standard Moodle. It is then soon lost. Webcrossing has had this power for over a decade, and I missed it when coming to Moodle.
And once the forum has a few posts, then keeping track of the files there is hard. For example here in Moodle.org, there are hundreds of files, but not way of seeing them in a list. Certainly no way of 'harvesting' the good stuff. There is a difference between a nice thought out item and a quick one off answer to a query.
In the forums, Even something very simple like this would be good:
1. At the post level: Attatchment field, Optional description field at the bottom of a post and then
2. "Display all files attatched in the forum" function
Filename - Date - Poster - Link to forum post