Here is a low cost and simple circuit that can be used to power up small electronics devices. The power is directly tapped from the mains via resistor R1.D1 rectifies the voltage and C1 and C2 are used to filter the output.The zener diode D2 keeps the voltage at steady 5V.
This circuit can deliver only up to 2omA ,there fore not suitable for serious circuits.
You can use this power supply for small LED circuits etc .
Remember you are playing with mains.Always be careful.
source : www.circuitstoday.com