The following are instructions for a pop up flash diffuser that can be printed and made with a single sheet of printer paper. It does not require any tape/glue, and can be folded flat for storage.
1 sheet of printer paper (card stock might be better)
1 pair of scissors
1 piece of aluminum foil (optional)
Step 1: Print, Cut, Fold
Cut along the solid lines, Fold along the dotted ones (using a ruler can help make a nice fold)
To attach the diffuser, start by insetting the long front tab into the hot-shoe.
Insert the two rear tabs on top, and VOILA!
Step 3: Optional Reflector
If you want to use the diffuser to bounce more light off the ceiling for a more natural look, simply cut a 6cm by 10 cm piece of aluminum foil and hook it onto the diffuser.
Step 4: Shooting
Install your diffuse and shoot, you shouldn't have to fiddle with any settings.