Automated mailing lists using taxonomy & custom user profiles

I'm running a simple Drupal site that carries articles on various topics. It's being run for an organisation that receives press releases which it then collates and puts onto the site, and also forwards to different mailing lists.

What I want to do is to collate these two operations, so that once a week the site sends out emails to mailing lists. Depending on what people have signed up for in their user account, they will receive different emails. So if they've signed up to receive information on "Cats", they will receive snippets on articles categorised as "Cats" under taxonomy; if they've signed up to receive information on "Cats" and "Dogs" they will received snippets on articles classified as "Cats" *and" articles classified as "Dogs" in toxonomy.

Are there modules available which can do this? If not, how difficult would it be for me to write my own module that would do this?