Now really diffusers don't cost too much. A Gary Fong Lightsphere will cost you about $40. But we have other things we want/need to spend $40 on. Well you're in luck! There are plenty of tutorials out there if you're up to making one yourself. And depending on how innovative you are, you could score one for free.
I thought I might need one for an indoor session I have tomorrow. I looked around in the cupboards and found a rubbermaid squarish drink conatainer that had been missing it's lid for some odd years. I carefully cut away the bottle mouth and then traced my flash over the reminaing hole. Then cut away again carefully until my flash could be slid in snug. Here's my flash bounced off the ceiling with no diffuser and then using the difusser at the same settings, both sooc.
other flash fun:
And what about making one for your pop up built in flash out of a claer film canister (if you still have one around?)