If you are using a portal like the one from @Brogan you can also save yourself a lot of work and let your members register to google feedburner, which sends out a small email when you post news to your site.
Demo: open a random front page article here and see the subscription box at the bottom of the first post (doesn't show on regular forum posts, just on the content you feature).
I choose Feedburner as it doesn't end up in the social and advertising filters of gmail like some newsletters do that i have subscribed to in the past (and never check anymore because of zero visibility).
Conversion rate so far has been more than promising. Simple solution, very positive effect.