USB is being implemented as a power connection standard more and more these days, but you don't always have a computer on hand so how are you going to power all of your sweet USB devices? How about a high quality switching 'wall wart'? This AC to DC power supply will do 5V at 1A! They're switch mode power supplies which means the output is regulated to 5V.
These have a standard USB 'A' connector for the output so you can power your Arduino, Raspberry Pi, etc. through a USB cable. Any device that uses a USB cable for charging or power can be powered with this supply.
Note: This works with 100-240VAC inputs.