RSS feeds, which enables you to “push” content to users is useful (subscribers can get your feed directly to their desktop if they want) and a bit cumbersome. It doesn’t publish on a set schedule, and relies on the poster to maintain a continuous cycle.
News sites often group their feeds according to topic as you can see here, which enables the subscriber to get feeds for the stories they want without sifting through stuff they don’t care to read.
Email, like RSS feeds, will bring news to the subscriber. It was used during the 9/11 terrorist attacks, with newsrooms using it to update subscribers as events unfolded. This enabled people to stay informed even when news sites crashed under the weight of web traffic.
One consideration with email is whether to send full stories or a teaser with a link to the story. On one hand, emailing the full story means readers don’t have to leave their inbox. Conversely, an email full of files is bulky and may get caught by the spam filter.
SMS technology (which, here, also included electronic billboards and RBDS) has the same instant-use as email, but far less space: usually 140-160 characters. In these cases–whether to a phone, a billboard, or the car radio’s face plate–the rule of thumb is: keep it to important stuff, and keep it SHORT.
Newsrooms and micro-blogging sites like Twitter can attach links to the full story to the SMS. For billboards and RBDS using stereo face plates, the key is to mention where the reader can get more information.
In every one of these cases, though, the bottom line remains the same: not every technology will work for every story. Choose the media to fit the story, not the other way around.