This is an email based group collaboration app. Here is how it works:

1. Send an email to <your group>@postosaurus.com and CC people you want to invite.
2. Start emailing your group using the new list you just created.
3. That's it.

Postosaurus will automatically version control any attachments you send to your group.
You also get a searchable index of your discussions and a view of all the attachements
and their revision history.