So after a couple months of various solutions, I think I found one.
Yahoo group functions I want to replicate:
-The look and feel of a central location for files and mail postings/exchanges between group members. I'd like to have even more flexibility of look and feel and of course no ads.
-The Yahoo Groups mailing list feature: not only can the group participants email the the mailing list address and that gets disseminated to all users but also gets posted to the group's web home for viewing on the web when a user isn't near a PC, and also where messages are also archived.
-A place for file storage (maps, documents, spreadsheets, pictures etc)
-Links to various sites
So after sdayman's and other's posts in my thread, I got to working with the other one click installs available through Dreamhost.
Wordpress seemed a good place to start: multiple users can post/blog. It is highly customizable (I'm learning more PHP too!) as well when it comes to look and feel.
More importantly, you can post by email. But Wordpress' Post By Email seems kludgy. You create a "secret" mail account and send email to it and it will be posted. Not so fast, you need to make a call out to/execute the wp-mail.php script to get the entry to actually post to the blog. (Wp-Mail.php goes out to the email account, logs in, grabs any email there, and publishes it).
Wordpress has issues sorting out different people making blog entries and attributing their post to the right author.
Wordpress also doesn't send an email to other authors that a post is made very well.
So I tackled it another way.
I created a mailing list on Dreamhost with five participants (four test email addresses and the secret email address I created for posting via email to Wordpress)
I setup all four valid e-mail addresses as users in Wordpress with Author rights.
I solved the wp-mail.php activation issue by creating a cronjob that calls wp-mail.php every 3 minutes.
One last item that was needed was that I needed to extend Wordpress' post by email capabilities. Did this using Postie, a WP plugin. This not only solved some formatting issues that occur when an email is posted as a blog entry (WP natively can't handle Rich Text or HTML messages just Plain Text. I know, maybe not such a huge issue but I'd rather not have to tell the other group members to check their mail format before they send...a couple folks are not hugely tech saavy), but also now correctly attributes a given entry to the right author.
Now, the whole thing comes together:
1. A group member sends an email to the mailing list email address;
2. The Mailing List Daemon does its thing and sends out the email to the other three list members as well as the "secret email address" used for WP.
3. The other members get the email just like an ordinary mailing list;
4. Within three minutes that message is also posted to the blog site attributed to the correct group member.
I'm in a testing stage. Sending multiple emails and replies to the list from all four email addresses to see if I can break stuff.
So far so good.
It took me a long time to setup because it was a pilot program, but once it's setup, I imagine I could write up some instructions.
I would likes some feedback from the community.