In that one, you set up a group and invite people to join, but group administrator can also manually add people. You can also decide whether the group is public or not. It's free. (They have it labeled as Beta right now, so I don't know the long term plans. I'd think it would be hard to start out as free and then change to fee-based later.)
I thought I read up here somewhere where there is a website that you can create where you can add people to the site whereas yahoo.com you have to invite the people to join. If you know the site please email me at This email address is being protected from spambots. You need JavaScript enabled to view it.