I had an original plan to be something else for Halloween, but then because of time constraints and school decided to go with an easier project, a head of myself. Sorry about the low quality images... only got my webcam working at the moment.

EDIT:
I forgot to mention this, but I got the idea from this guy: Eric Testroete, who apparently got it from someone else but I saw his so I'm gonna stay with that :P

EDIT 2:
Someone pointed out that there was already an instructable for this so I'll link him on here as well: Real Life Big Head Mode

Step 1: Ingredients

Items needed:
3D program - modeling and able to export OBJ file
Pepakura - to change the OBJ file into cuttable paper images
100 lb cardstock - needs thick paper so that it'll hold the shape
Sharp scissors and Xacto Knife - for cutting paper... be careful
Super Glue/Hot Glue Gun/Double stick tape - to put all the pieces together

Optional items:
Resin or Casting Plastic - to harden the helmet
Foam Padding

Step 2: Modeling

Ok so first things first. You will have to learn how to use the 3D program to model and texture your face. I'm sorry but you will have to learn this on your own since this step could be an instructable on it's own.

Here's a good video on how to model the face using Autodesk Maya:

http://www.youtube.com/watch?v=xls25e08sSg

After you finish the model, export it out to OBJ file so that Pepakura can use the file.

Step 3: 2D-ify - Part 1

Ok now to bring it into Pepkaura. Open up your file and there will be a few little steps that follow. I usually skip those since it's pretty much set the way I need it to be, but for those who don't have it exactly right: (look at pics below for reference)

1) First one just says how many verticies, faces, objects, etc. not really important
2) Flip faces, don't wanna do that so "No Flip"
3) Now it's asking which side is the front. If the first image you get with the arrow pointing out is right, then just click "Next"
4) Same as before but with the bottom
5) Invert the Model? That's a no

Ok after all of them you'll be left with just your face. When you move your mouse over the model you'll notice that the edges turn green. At this point you are in cutting mode. Click on any edge that you want "cut" so that it will be easier to piece all the parts together.

For example I cut my face outline and around the headphones so that I will have a separate piece for the hair, face, and headphones, which I attached later.

Step 4: 2D-ify Part 2

Now to make sure your paper sizes are all correct. Click on the menu options "Setting", then "Print and Paper Setting...". Next a window will open. Make sure that you have the right size paper set. I'm in the US so I use "Letter" size. Then click "Ok".

Ok next, this is where the magic happens :D and why I love this program so much :P
Uncheck the "Auto" checkbox next to the "Unfold button". The "Auto" makes it so that it will cut the model up to fit one sheet of paper... which will give you a very tiny model.

Now click "Unfold" and a window will show up. Measure how high you want your head helmet to be. Make sure that you make the model bigger than your head, so that your own head will be able to fit inside. I made mine about 6 inches taller. All the other measurements will scale out. Finally click "Ok".

After a couple of minutes you will get cut up pieces on the right side of the screen. Arrange all the pieces so that they mostly fit inside the dotted lines. You can also "Right click" and "rotate part" or spin the parts around.

Now there are a couple options once you're done arranging it. Click on the "2DPatternWindow" menu option and you will see them.

Overflow Paint makes the texture on the model go past the lines so that it spill onto the glue tabs, which will help in the actual making by decreasing the amount of gaps appear along the edges.

Show Edge ID will create little number on the faces that will help you match up the other pieces. I didn't do this just so it'll be cleaner, but oof it took me a while to assemble.

Show page number adds the page number to each of the pages.

And the rest you can figure out since I haven't tried any of them XD.

Finally print it out. Oh! Almost forgot. You can either print this on your own computer, or print it out to a pdf so that you can send it to different print shops and let them print it. I sent mine to Kinkos which cost about $25.

Step 5: Tape, Cut, Repeat, Assemble

Now the grueling part of the project. Cut the parts out, remember solid lines only. If you have a part that is on two pages, align them up with each other and tape them. I used clear packing tape, wish I used matte tape so that it didn't shine so much.

Then following the edge ID or your computer, match up the pieces that attach them together with the tabs. For this step I used double sticky tape, but at times wished I used either super glue or a hot glue gun. Experiment to figure out what you are comfortable with.

Sorry for the lack of pictures, was busy cutting and assembling away that I forgot to take pictures.

Step 6: Finalization

Once your model is all assembled, you are pretty much done. Only other options you have at this point is to strengthen the model so that it doesn't break or something. There are two options that I know of for this step.

Method 1 - Resin and Fiberglass
There are a few different tutorials online which I've found and this is the preferred method. Remember that resin gives off fumes so do this in a well ventilated area. Also wear thick gloves when working with fiberglass, it's pretty much glass that is thin like thread so if that goes in your skin = bad end.

Method 2 - Plastic Casting Compound
This method is safer, but a little more pricey. Smooth-Cast 300 is a two part compound that when mixed together becomes white hard plastic so use this on the inside of the helmet.

I still have to do this final step.

Other than that I can't think of anything else more to say so have fun and be safe.