Basically, online PR is about influencing online media, communities, bloggers and web assets such as search engines, news search, forums, discussion threads, social networks and others.
Popular blogs are often as influential as regular print media. Only they have no editorial calendar nor carry press release as is. Instead they prefer to write a small post while providing a link to the press release
The trick in online PR is to make it easy for online media to find out about your news. Keyword optimized press releases, distribution via wire servies, an online media kit, a keyword optimized blog plus strong SEO are other essentials.
While software tools do help automate and research it is the human analytics that provides the necessary edge.