i will show you how to make a led blink and use a usb port of the computer as a power source.

Step 1: Materials

What you will need:
1] 555 timer
2] 1k ohm resistor x2
3] 100 ohm resistor
4] led{any color i used a green}
5] capacitor [depending on the blinking rate. see next step}
6] circuit board
7] usb male connector
8] 555 timer holder {whatever it is called}

Step 2: The Capacitor

you can use any capacitor in the range of 10uf to 1000uf depending upon the blinking speed.
if you take a capacitor of less value will blink the led faster.
if you take a capacitor of more value will blink the led slower.
i used a 100 uf capacitor.

Step 3: Solder the Circuit

here is the circuit digram . solder the the circuit according to the digram.

Step 4: Connect the Usb Connector

we will need only the red and black wire.
my connector had red and a blue wire.
connect the red wire to the positive terminal of the blinking circuit.
connect the black wire to the negative terminal of the blinking circuit.