Whether your working on electronics, want to test that speaker, checking out a cool looking radio at a swap meet, want to soapbox the evils of soapboxing, or sit on the street corner singing your blues ...
Well, darnit, sometimes you just need a simple easy to use amp!
I bring to the world Pocket Protest (a LM386 amp in a 9v battery casing)
Pocket Protest runs on a standard rectangle type 9 volt battery for a couple hours and can power a 4 - 8 ohm speaker fairly easily, while all along being enclosed in a 9 volt battery casing
The wattage is low, but since theres no filtering or enhancement the sound that comes out is quite brash...
Its a can running off of a 9V battery, and it sounds like it too! Even if the wattage is low the "bullhorn" quality sound gets loud enough that normal people have to talk to almost shouting levels in order to speak over the device
Here is a video of the breadboard test mentioned in step 9, with a really flat tiny 25 watt 8 ohm speaker, it was around 30% volume, which was enough to overdrive the mic on the camera and my wife on the other side of the apartment http://cheesefactory.us/filecenter/PDR_0002.mpg