What's the best way to advance your knowledge in your field without getting an additional degree?

For instance, I work in the m communications field, but because I had a scholarship to a small liberal arts school and wanted to maximize my future career options, I majored in English. Now, I want to gain some new perspective, since communications is rapidly changing because of social media & the like. Professional seminars seem overpriced and redundant to info I can learn out of a book? Are there ways to just take academic courses you need without going "whole hog" on getting a different (and expensive) degree?