I’ve been wanting to share files between me and my wife’s account on the Mac, but have not been able to do so. I’ve finally found the answer using ACL’s. It’s very easy to do, just follow these steps for every account you want to make accessible by others.

  1. Open up a Terminal (Finder -> Applications -> Utilities -> Terminal)
  2. Execute the following command from the prompt, notice that the leading # is not part of the command, and that <username> tag should be replaced by the “short name” of the users whose files you want to share. 
    find /Users/<username>/ -exec sudo chmod +a# 0 'staff allow add_file,add_subdirectory,list,search,readattr,delete,delete_child, writeattr,writeextattr,file_inherit,directory_inherit' '{}' ';'

  3. All accounts on the machine should belong to the staff group and have full access to this users files.

You can modify the command to fit your needs, for example lets say you only want to share Pictures change "/Users/<username>/" to "/Users/<username>/Pictures/"

If you only want admins to be able to have permissions change +a# 0 'staff allow to +a# 0 'admin allow