How to implement 'category' based newsletter

Working on my small classified site; i'd like to give the users the ability to choose some categories, for example : cars, boats and receive daily/weekly notifications based on their choices.

A user that has subscribed to 'cars' category will receive daily newsletter saying 'there are 30 new interesting classifieds for you in category : cars'.

Don't know where to start; 'simplenews' module seems too simple f开发者_如何转开发or my usage.

Any idea ?

The Subscriptions module seems to do this really well. It will allow your users to select categories they wish to subscribe to as well as the interval they choose to receive notification emails.

As an administrator you can set default category subscriptions for users (if you wish) and to send notification emails in digest form (multiple updates in one email). It doesn't have a time interval of 'weekly' but you may be able to request this in the module issue queue. It is very configurable.

Have you checked out http://drupal.org/project/notifications module?

It's not the easiest module to get your head around but the rewards are pretty good. If you categorising your content using taxonomies then this module should help.