for the link Steve. Have bookmarked the site. FYI rubbing alcohol makes a good glass cleaner.
Keep in mind that any diffuser works by having indirect light striking the subject after bouncing on surrounding walls, ceilings or other surfaces. Which means it can be highly effective in small rooms and only lose intensity in large rooms.
I don't use external diffusers, only the built-in one in my Canon 430. However... I have fitted a scratch attachment on the rear of the flash. This enables me to stick a small white cardboard rectangle as a reflector. When the flash is oriented to bounce on the ceiling, part of the light is bounced directly on the subject, you get a mixture of direct and bounced light. You can vary the surface of the part of the carboard by sticking it lower or higher.
- low: you get just enough direct light to add catchlights and avoid 'racoon eyes'
- up: You get balanced lighting, and the surface of the reflector is superior to that of the flash head or most reflectors, which gives less sharp projected shadows behind people.
Costs nothing. Plus it's a trick used by many pros... you won't be considered an amateur or 'an uncle Joe with its Rebel' any longer!
http://www.prestophoto.com/photos/image/1028231/21411