Getting media exposure for your business is immensely valuable. You get a trusted authority, such as a newspaper or television program, talking about your brand. Yes, you can buy advertising space, but (a) it's not very zero budget and (b) it's YOU saying how good you are, not someone else.
But it's a hit and miss operation, with PRs flogging their client's products to the media on their own schedule rather than on the media's. And if you want to do your own PR, you're likely to have a lot less of the relationships these PRs have, so it can be even harder.
That's why a SourceBottle (free) email subscription should be on every business owner or marketer's should be in your inbox. It's a great little online service that connects journalists, writers and bloggers with 'sources'. They do this by emailing 'call outs' for sources from journalists, writers and bloggers to subscribers to the service. They help journalists, writers and bloggers connect with an extensive network of quality sources; and they help subscribers to the service get publicity (or famous, whichever comes first).
So you get to respond to requests when journo's WANT to hear from you. I can't imagine I'm the only person who's excited by this prospect. So far I've come across several great leads for clients AND friends, for everything from promoting a shopping site on another online service to getting a product reviewed for a magazine article.
SourceBottle's revenue model seems to be in some advertising and premium subscriptions, which still seem extremely cheap. So I hope they'll stay around for a long time, it's zero budget marketing gold.