I use a piece of white 'funky foam' cut to the
better bounce card shape, attached with an elastic band. The foam is available from craft shops for about £1 for an A4 sheet, and you could easily buy a piece of wide black elastic to make a more professional-looking attachment band than my pink rubber bands dropped by the postie!
There is a video on making and using it
here if you can bear to sit through it all - he does go on and on...
I find it really good, even if there is no ceiling/wall to bounce off. You can adjust the size by folding it back or sliding it up and down the flashgun. It is durable, weighs nothing and tucks into your camera bag easily.
brilliant idea mate , thanks for such a detailed reply
You could try it out first with some white paper.
I usually put a piece of black foam behind mine so that people behind me aren't disturbed by the flash showing through the translucent white foam.
I've also tried making the stofen type by cutting the bottom end off an empty Ecover washing-up-liquid bottle, but I prefer the results from the foam bound card, and it is more flexible in use.
It is really easy to use with a Nikon. I set the camera to manual, choose a shutter speed and aperture and fire away, letting the camera look after the metering (use TTL). Of course you lose some light by bouncing so you may need to increase ISO.
Hope this helps.