I saw a guy at a wedding last weekend with this frosted globe thing over his flash, and he had it aimed straight up. most of the flash would hit the ceiling and bounce back, but some got caught in the frosted plastic and softly illuminated targets. Dunno if its the same kind of thing as this, but I liked the effect it made. Similar to what the sample pics on that site showed.
A built-in flash just isn’t going to have the required horsepower to bounce successfully in a lot of situations. If you stick to High ISOs and small F stops it might be somewhat useful, but a real external flash is going to give you orders of magnitude more flexibility.
I’ve used a ping-pong ball with a slit in it as a cheap diffuser for a pop-up, but never tried bouncing. I’m sure with a little redneck engineering, you could make a similar device for much less than $35 (although that’s not terribly much to begin with) and play around with the effect.
orionid you pretty much said what I was thinking about making my own version just to try the whole bounced flash thing. Over the last couple of days I have gotten the same advice about the popup flash in general.