Again, nothing's new under the sun... My DIY is just some modifications of Chuck Gardner's here:
http://super.nova.org/DPR/DIY01/
Mine is only significantly different in that I added "cross-stitch matrix grid," "metallic silver", and upcoming "gold," reflectors that are easily interchangeable by velcro inside the "white" default reflector. Other minor differences are that instead of stapling around the edges, I used velcro to connect the inner white to outer black "fun foam," and used an iPod "exercise band" that is useless for my iPod use but perfect for this DIY. (I never throw away such "useless" things since you never know what DIY projects might come up. )
1) Diffuser-Reflector on Flash - Front View with "Cross-Stitch Matrix Grid." (Note that the top can bounce off its own "roof" which is useful when shooting in situations where there's no ceiling to bounce off of, as in outdoors or indoors with unreachable ceiling. When ceiling is available, the top can be angle-adjusted to open up towards the ceiling.)
2) Diffuser-Reflector on Flash - Back View