This month's edition of Internet Works magazine has a huge feature called PR Masterclass, which is well worth a read. As the magazine puts it:
"Public relations is an underestimated marketing skill. [By reading this feature] you'll learn all about creating and sending press releases to get your company in the news, and we'll show you other PR opportunites to try."
Also, my comments on sourcing a PR agency are featured in the article. Ooh the glory! The full piece isn't online unfortunately.