> My group of volunteers has no funding, so very cheap, preferably 
> open-source suggestions are most appreciated.

Just curious, but what group? What's its purpose? If it is an open
source software project, SourceForge will of course provide these
services and many others. I vaguely recall projects on SourceForge that
didn't even have code, rather were centered around documentation or
education or something. Ah, here's one:
http://sf.net/projects/slrn-doc/ .

I also use Google Groups (free as in beer, not speech). They provide a
decent service.
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