I followed the circuit diagram I had printed from someones website (sorry, can't remember which one).
I'll draw it up and place it here soon, along with pictures...
The parts are:

• 1 - 555 timer chip
• 2 - 1k resistors
• 2 - 4.7k resistors
• 1 - .0047 micro-farad capacitor
• 1 - .01 micro-farad capacitor
• 1 - Green, low-power LED
• 2 - Handles: 1/2 inch diameter, thin-wall, brass tubes, 4 inches long
• 1 small project box from Radio Shack
• hookup wire
• 1 - "wall-wart" power pack (120vac input, 7.5vdc output)
  (Note: This actually measures 10.5vdc, nice clean DC output!)

They connect like this (from pins of 555):

1. to V- and one handle (negative or ground)
2. to pin 6 and R2 (4.7k), to pin 7
3. to R3 (1k), to R4 (4.7k) and one handle (positive),
   R4 (4.7k) to cathode of LED1, anode of LED1 to V-
4. to pin 8 and R1 (1k), to pin 7
5. to C1 (.01 mfd), to V-
6. to pin 2 and C2 (.0047 mfd), to V-
7. to R1 (1k) and R2 (4.7k)...
8. to pin 4 and V+

Circuit Diagram:

To the right, is the finished zapper. The power-pack, to the right, and the handles, above it.
Here is a test setup using the o'scope, the black probe is stuck in the zapper. Also a meter to measure my resistance when holding the handles. Notice the third handle, the right-most, is only connected to the meter and not to the zapper. I measured ohms between this spare handle and one of the zapper's handles. I moistened my hands with water, then held the handles to see the resistance.
Here's a close-up view of the insides. The 555 chip is in it's socket, which is soldered to the little PC board. Everything except the power-pack and the brass tubing for the handles was to be had at Radio Shack.

Scope Results:

Below, is what the scope program looks like,
it's hooked up to the Zapper running with no load.
The scope has 2 channels, here I'm only using channel 1.
  
The volts/division is set to 2 volts and the time/division (horizontal) is at 10 micro-sec's.
The vertical, dashed lines allow measurement of timing and frequency.
Notice that the frequency is 27.83kHz and cycle time is 35.94 micro-seconds.

The horizontal, dashed lines allow measurement of voltage between them,
it shows my pulses peak at 7.13 volts, RMS is shown too, at 3.50 volts.

Next, see what happens to my square-waves when I load the output:
This, below, is the result of lightly holding the handles (my hands were moistened with water).
The resistance thru me is about 400k ohms, handles disconnected from zapper and measured with DVOM.
The pulse now peaks at just over 6 volts.

Now, when I tightly grip the handles and the resistance reduces to around 40k ohms I got the following trace:
The pulse is only about 3 volts, riding on 2 volts.