Columbia Journalism Review

From their website:

CJR's mission is to be the intellectual leader in the rapidly changing world of journalism. It is the most respected voice on press criticism, and it shapes the ideas that make media leaders and journalists smarter about their work. Through its fast-turn analysis and deep reporting, CJR is an essential venue not just for journalists, but also for the thousands of professionals in communications, technology, academia, and other fields reliant on solid media industry knowledge.