There are plenty of way to have “automated” newsletters sent out based on your WordPress blog’s RSS feed. Feedburner and MailChimp, among other do this, and there’s nothing wrong with those services.

However, if you’d want to write content specifically for your weekly e-mail, RSS is not ideal. High quality e-mailings usually don’t simply copy blog posts, they’re carefullt crafted by copywriters to get as much response as possible. That’s why the idea of a newsletter-theme has been floating around in my head. Here’s what I’m thinking might work…
More Idea: A WordPress theme for e-mail newsletters?