How to share a personal blog to a group ?

Hello everybody,

I would like to make possible for users:
1-  to write blog articles in their "own container" ;
2- if they want to share it later to one or more groups. 

It could be the same for photos, bookmarks or files.
Is it possible ?

How do I have to do :
1- to save it in the DB ?
2- to display it in the group dashboard ?

Does it need the "relationship" function ? 

Thanks for your help,