I have a good flash for my DSLR but I’m always reluctant to take it out of the bag, mount it on the camera and carry the heavy package around. After reading something about a business card taped on your flash as a free diffuser, I tried it.
Take some white cardboard and cut it to the following dimensions. The dimensions are for a Canon EOS 400D but the principle should work for any camera with a hot shoe. Fold the card on the dotted line and strengthen the bottom part with tape.
That’s all there is, really. Open the flash, slide the card in the hot shoe and start shooting. See the difference? The first photo is without a diffuser card, the second one with diffuser.