The discovery of the accelerating expansion of the Universe has precipitated a crisis in fundamental physics that lies along the intellectual fault line between quantum mechanics and gravitation. We have given the name "Dark Energy" to the origin of the gravitational repulsion that is driving this accelerating expansion. Dark Energy evidently comprises about 75% of the cosmic inventory. We are living through an intellectual revolution that has many parallels with the advent of quantum mechanics, but it's unclear when we will achieve a breakthrough in our understanding. I will review the current state of Dark Energy observations, and sketch out some possible scenarios for the future.