This is a comment about Groups.io from the fboats site - looks good but looks vulnerable at this stage in its development. Maybe picking up enough Yahoo transfers will make it a larger less vulnerable company.

"Group.IO PROS:

I own/moderate several Yahoo groups and I have been testing groups.io.  I built a small test group recently.  I bought a paid subscription to get a small gtroup which is presently waiting in the queue for transfer, in order to test the process. I also have been running a free a forum and I am testing the backup/export capabilities. 

Based on my testing, I can confirm that GROUPS.IO can accomodate  files and photos, both inline and as attachments.  All can be backed-up in their native file formats.  Messages can be archived in mbox format.   

So far, I like what's been happening but I am still waiting for the transfer of the one group, so the jury is still out. 

Group.IO CONS

Groups.io is a one man show, literally.  The support community consists of one company owner and two volunteers.   While I have found the support team to be very responsive, and the product robust, the risk of them going offline is great. There is not a stand-alone version of the software. "