3.5 mm connectors, RCA connectors, TOSLINK connectors and XLR connectors are common speaker connectors. According to Cables To Go, these connectors are used for home theater and portable use to audio mixing boards for DJs.
3.5 mm connectors, also called 1/8-inch connectors or mini-plugs, can be used to carry up to three signals and are often used for portable devices and computers. RCA connectors are used for many audio applications, including transporting the analog composite audio signal to the left and right audio for dual channel stereo audio. TOSLINK connectors were initially intended for Toshiba CD players, but have been embraced by other manufacturers and are used for A/V sources, surround sound equipment and receivers. XLR connectors are used for professional audio applications, including microphones, amplifiers, mixers and other professional audio devices.