A soap dispenser can be configured to dispense an amount of liquid soap, for example, upon detecting the presence of an object. Certain embodiments of the dispenser include a housing, reservoir, pump, and nozzle. In some embodiments, the dispenser includes a bypass passage, which can facilitate priming of the pump. In certain embodiments, the dispenser is configured to inhibit or avoid the formation of an air bubble that could obstruct the liquid soap from entering the pump. In some embodiments, the pump includes engaging gears, which can include a plurality of teeth with substantially pointed tips. In certain embodiments, the nozzle comprises a one-way valve, such as a duckbill valve. Some embodiments of the one-way valve are shaped or otherwise configured to provide certain biases to the valve, which can, for example, facilitate rapid opening and closing of the valve.