Pololu 5V Step-Up Voltage Regulator U1V10F5 This tiny (0.35″×0.45″) U1V10F5 switching step-up (or boost) voltage regulator efficiently generates 5 V from input voltages as low as 0.5 V.
Pololu 3.3V Step-Up Voltage Regulator NCP1402 This compact step-up (or boost) regulator generates 3.3 V from voltages as low as 0.8 V and delivers up to 200 mA, making it perfect for powering small 3.3 V electronics projects from one or two NiMH, NiCd, or alkaline cells.
SparkFun Variable Load KitThe SparkFun Variable Load Kit is a quick-to-assemble board designed to allow users to draw a specific amount of current from a voltage input. This kit can be used to test stability of the power supply under various loads, battery lifetime, safety cutoffs and other design elements.
AC-DC 220V to 5V 700mA Power Supply Buck Converter Step Down Module
AC-DC 110V/220V to 3.3V 700mA Power Supply Buck Converter Step Down Module