Connect your MP3,iPod,Laptop,Cell Phone... and you got your self a DIY portable stereo.
It can be powered using batteries and be helpful in many cases.
It is capable to drive a small 8 Ohm speaker or even a combination of a small in diameter
say 2-3 inch woofer and a tweeter for better acoustics.
Step 1: The main ingredient
Let me stay here and say that I'm not the Columbus, who discovered America!
There are plenty of information out there, just type LM386.
To begin with...