David Meerman Scott has published a free eBook titled New Rules of PR. You can download it from his blog post.
In the PDF, he talks about how Press Releases have changed with the evolution of the Internet and offers some great suggestions for how you can get your content to do some heavy lifting for you and increase sales. He also provides some great ideas for things you can write a press release about that may not have ocurred to you.
David says, "The media has been disintermediated. The Web has changed the rules. Buyers read your press releases directly and you need to be talking their language."
The eBook talks about promoting your expertise and gives some great tips about how you can make your press release drive traffic to your web site. It's all about content and what you can do with it.
Go read it.