Posterous Groups is an attractive and easy-to-use group collaboration tool allowing users to keep up to date with groups of friends, family or co-workers through email as normal but have it stored and accessible via Posterous. (It's sort of like a friendlier variation of Google Groups.) Images, video, other embeds and attachments are all accessible from a group's optionally private Posterous portal.
Keeping their theme of simplicity, group sign up only requires an email. Once registered, your friends and family will receive an invitation through email. After accepting all updates made to the group via Posterous's web portal, or from a users email will be shared with the rest of the group members.