  The discovery of cosmic acceleration has raised the intriguing possibility
that we are witnessing the first breakdown of General Relativity on
cosmological scales. In this article I will briefly review current attempts to
construct a theoretically consistent and observationally viable modification of
gravity that is capable of describing the accelerating universe. I will discuss
f(R) models, and their obvious extensions, and the DGP model as an example of
extra-dimensional implementations. I will then briefly describe the Galileon
models and their very recent multifield and curved space extensions - a class
of four-dimensional effective field theories encoding extra dimensional
modifications to gravity. This article is dedicated to the career of my friend
and former colleague, Joshua Goldberg, and is written to appear in his
festschrift.
