1. Start creating a new RGB image. I used the dimensions of 288x288 in the example.

Click on the rectangular marguee.

Make a one pixel line (which is going to be your main bar code line)

Fill the whole selection with the color of your choice.

2. Click on Filter > Noise > Add Noise.

Change the amount to 400%
Distribution: Uniform.
and Check the Monochromatic option

Hold CTRL and hit T. Then drag it upwards.

This will give you something that looks like the image on the left.

3. Using the marquee tool again, cut a little from the bottom.
And add your text. =)