This is the answer to my own question - I figured it out with the help here and a little experimentation.

The Sony Alpha camera, when used with one of the WL equipped Sony (or Minolta too?) flash units can fire wirelessly using something they call HSS - or high speed sync. In a nutshell, HSS is a code sent from the camera to the flash, telling it to fire. This code is not sent via infrared or radio - it is actually transmitted within a pre-flash sequence of flashes directly from the on board pop up flash. The on board pop up flash cannot be used in conjunction with wireless (as far as I could determine).

Setting it up -
It's really simple once you know how...

1. Turn on the camera and flash unit - the flash unit does NOT have to be on the camera for you to set up wireless... probably better if it isn't.

2. Turn on the wireless (WL) button on the flash - assuming the flash unit is not connected to the camera, it's HSS light should also come on automatically. You'll notice the sensor in the front of the flash blinking a bit to indicate it's ready. (If you happened to have the unit on the camera, the HSS light would not be lit, because the camera/flash connection then becomes hard wired.)

3. Find the on camera flash menu. (On the A300, it's under the FN button.)
Select flash type - WL (wireless).

4. Position your "ready" off camera flash unit anywhere away from the camera, but not really far, just where flash assistance is desired.

5. Go ahead and shoot. You should see your on board flash send a machine gun burst of pre-flash, milliseconds before the shutter goes off. In turn the external flash fires as your shot is taken!

One odd thing I encountered - if I set up the wireless setting in the camera, and then changed from one shooting mode to another (ie. Auto to Manual), the WL setting was lost and I would have to go back into the flash menu and set it up again. Makes no sense, but that's what happened.

Another thing I found when playing with it on a desktop...when the camera and flash unit were very close together, the external wouldn't fire. I'm not sure if that was because the camera and flash unit were too close to one another, or that it was sensing enough light to not need a flash. Don't know, but it might not work for you either under similar conditions...

The ease and flexibility of this is very nice. The only drawback I see it that once you get it working, you'll want to buy more flash units, stands, umbrellas, soft boxes etc. LOL

Have fun!

PS - Make sure to turn OFF the WL function on your camera after you use it.