One of the hottest issues in PR and communications today is “social metrics“. As Web-based measures rapidly replace older measurements associated with “mass” media, social metrics is now a key component to communications strategies.
For a general overview see “Why You Need to Monitor and Measure Your Brand on Social Media“. On metrics, see “Web Metrics 101” and “5 Digital Marketing Metrics that Matter“. For more specifics, see “5 Social Media Metrics You Should be Monitoring” and “3 Social Media Metrics Your Business Should Track“.
For the basics on SEO, see this Wikipedia defintion of SEO (search engine optimization). One of the more recent trands has been the merger between SEO and PR. More more on that see “Why PR and SEO go hand in hand” and “The Importance of Search-Optimized PR“. See also “SEO and PR can achieve online success” and “10 Reasons Why PR is a ‘Must Do’ for SEO in 2013“. And read this article in Forbes: “The Death of SEO“.
On the “social sentiment” analysis see this article in the New York Times, “Mining the Web for Feelings, Not Facts” and “How Companies Can Use Sentiment Analysis to Improve their Business“.
Finally, a response to this question: “Measuring Social: Is It All Just Folly?“