A heat sink comprises a heat sink body, which in some embodiments is a plastic heat sink body, and a thermally conductive layer disposed over the heat sink body. In some embodiments the thermally conductive layer comprises a copper layer. A light emitting diode (LED)-based lamp comprises the aforementioned heat sink and an LED module including one or more LED devices in which the LED module is secured with and in thermal communication with the heat sink. Some such LED-based lamps may have an A-line bulb configuration or an MR or PAR configuration. Disclosed method embodiments comprise forming a heat sink body and disposing a thermally conductive layer on the heat sink body. The forming may comprise molding the heat sink body, which may be plastic. In some method embodiments the heat sink body includes fins and the disposing includes disposing the thermally conductive layer over the fins.