If you are an owner or moderator of the Yahoo Group, you can do some of what you mentioned. Click on Files on the left-hand side of the Group’s web page. There you can set up a File to automatically be sent to members once per month, automatically be sent to members once every two weeks, or automatically be sent to all new members (Upon Joining Group). It’s just once per week or more frequently that isn’t possible. And you’re not limited to just one File doing this either – you can have any number of Files automatically sent in one of these ways.