As usual, David Remnick has some of the wisest insights and most tightly crafted writing on the situation in Ukraine. And, unlike virtually everyone else writing and talking, he has a deep knowledge of Russia and the former Soviet Union. Worth your time to read.
This opinion piece by Charles King in the Times also made a lot of sense to me, not for taking a clear position but unfolding many the complexities and extreme dangers of the situation.
Meanwhile my friend Garance Franke-Ruta put together this curated twitter list of various people you'll want to hear from about the situation in Ukraine - journalists, foreign policy hands, observers, historians, activists.