I spend £5 on one of those cheap fold over flash diffusers for my E-510 built in flash. I found I could not get repeatable results with it from multiple shots. I then found the 'Gary Fong Puffer' on ebay. These seem to be tough and rugged. But the best part of it is they work fantastically. Every multiple shot the lighting is identical.
If your looking for an inbuilt flash diffuser then trust me : Dont spend £5 on a cheap flimsy fold over one - Spend £10 and get one that actually works.