Re: What kind of materials would I need to make a working CPU?

Well, to start from scratch you will need some sand, a furnace, a 1 part 
per million pure atmospheric environment, a some multimillion dollar 
molecular depositing equipment, a logic analyzer, and lots of Mountain Dew.

But luckily we don’t have to start from scratch.  A microprocessor has 
three major components to it 
1)	Memory.  This is a collection of transistors that can hold a state 
of ons and offs that represent binary numbers or instructions
2)	Athrithmetic Logic Unit. This is the unit that can do all of math 
and logical operations on binary numbers or instructions.
3)	Control Unit.  This is the component that reads in your program of 
instructions, and moves numbers in and out of memory, and controls the ALU.

For more detail, check out  http://electronics.howstuffworks.com/microprocessor2.htm.

Two of these three components can be purchased from semiconductor 
distributors in your area.  For example,  Fairchild Semiconductor makes a 
ALU  (DM74LS181).  Still, this project is more for a Masters Student in 
Electrical Engineering than for a science fair project.

Might I suggest a different path?  I used to sell microprocessors to 
engineers making all sorts of devices, from DSL modems to controllers for 
ovens.  They never made their own microprocessors from scratch.  I had 
demo kits for microprocessors that included the breadboard, the 
microprocessor, a display, and programming software.  The kits I liked the 
best included a PIC processor.  Your requirements for the lab will be a 
computer with a serial port.  Maybe write a program that turns on a light 
whenever the seconds in the day is a prime number?  Something fun that 
shows you were able to program the microprocessor.  Believe me, if you get 
a program to work it will be because you know EXACTLY how that 
microprocessor works.   Warning, this is probably a 9.5 out of 10 on the 
difficulty scale for science fair projects.  You will need to spend over 
140 hours of reading, programming, rereading, and reprogramming.  

A quick search on Microprocessor Kits on the web took me to 
www.gemtree.com.  They look like they have school discounts.  Talk to you 
math or science teacher about your project ideas and see if the school 
will buy a kit.  Also, find a good technical mentor to help you out with 
the scope of your project.

Have fun at the fair and good luck with the project!