Couple things regarding the 580EX catch light panel / AKA "white card". Some of the comments made about use of the white card in this thread want to make me reaffirm my understanding of it's use.
1 - When the when the flash head is angled upwards for a ceiling bounce for diffusion and light spread, I've been using the white card is as a means to fill in shadows and create a catchlight in the subjects eyes. This has worked well for me.
2 - When the flash head is angled upwards if there is a high ceiling or dark ceiling, or outdoors, the light directed upwards is essentially wasted. Some light reflected from the white card does go forward and illuminates the subject, but because the white card is near to the same size as the flash head itself, it does little to diffuse the light and you've reduced your flash range. Probably a Lumiquest might be a better solution in situation like this as it has more surface bounce area to diffuse from.
3 - I own and use a Sto-Fen occasionally. Works OK to bounce when ceilings are present and provides good frontal fill. Doesn't create catch lights in the eyes as well as the white card.
Sidenote about some other lighting methods I recently observed...
Recently attended a wedding and the photographer shooting was using a portable Lumedyne head with about an 6"-8" diffuser on the front. He was shooting a Hasselblad (with film!!) so no need to rotate the camera or flash. For every shot that I saw him take there was no bounce involved, only direct. He's been around for 20 or so years and his work is excellent.