Yep, you see some articles pay for the rest type of thing would work (like what ft.com do), give them the option of printing the article / email to a friend / send them an email when a new article is put up etc
Another option to look at is what wired.com do. They publish a magazine, in there on-line edition they allow you to view the first article for this months edition for free, you can see the blurb for the other articles but need to subscribe to see the articles there and then, alternatively, if you return a week later another few articles are viewable until all the articles are there and its time for next months magazine. (not sure if i explained it well but if you go here you can see what I mean
http://www.wired.com/wired/
(Just had a look at the site, they have changed how they do it, all articles are available from the beginning of the month)
This in my mind also works quiet well, as it gives you a reason to return to the website more than once a month (which is vital if you are advertising)
Also you could look at building a community by allowing people to submit there own articles or article suggestions, you could add a bulletin board, which could work well if you are aiming at a niche area.
The reason I have been thinking about this so much is because Im also looking into providing a news source aimed at a niche market that isn't being served currently. I have a guy doing some work for me at the moment on the website and we are looking at different options, for us the news is important but the community we plan to build around the site is essential for it to work.
PM me if you are interested, we may be able to share resources
Cheers
Fintan