Something just came to mind about diffusers ...
Quite a few diffusers requires some degree of skill/understanding to use effectively, so I would not suggest those.
You could try a Lembency (Gary Fong Lightsphere knock-off) diffuser which you out on and just use with the flash head pointed straight-up. Hehehe ... look for the youtube GF tutorials on how to use it for say portrait orientation.
Or a cheap Stofen knock off. I think you can get both these diffusers at OP, but if you get it online, it's probably much cheaper (at least it used to be when I got mine).
The stofen is effective only when there is a low ceiling to bounce off (it's used at 45 degrees) and the Lembency only when there are walls around you. Both diffusers will lower the efficiency of your flash quite abit, so pump up the ISO.
IF you REALLY want to make an impact, you could try this diffuser -
http://www.flickr.com/groups/strobist/discuss/72157603251265338/
Don't forget extra sets of fully charged batts and spare memory cards.