Three-coordinate boron, with its vacant p-orbital, is a useful pi-acceptor in conjugated organic molecules. These materials have interesting linear, as well as first- and second-order nonlinear, optical properties, exhibit two-photon-excited fluorescence and fluoride ion sensing properties, and can serve as emissive and/or electron-transport layers in OLEDs. Polymers containing three-coordinate boron in the main chain also display interesting optical properties. These features are all addressed in this short review.