DISCLAIMER: This project should not be dangerous. In event of injury because of the project, I cannot be held responsible. Honestly, though, how on Earth could you hurt yourself building LEGOS? Anyway, time to start!
Step 1: Parts
1x NXT Brick (main controller)
2x NXT motors
2x NXT port wires (medium)
1x Computer with NXT and LDD (Lego Digital Designer) software
1-2x NXT pieces kits
All you have to do is gather these supplies in a clean, open, space and you are ready to begin!
Step 2: Building the Wheel
1) Add a motor to the side of the main brick. It is the speed controller. (First picture)
2) Build a foundation on the other side of the brick and put the motor inside to power the wheel (second picture)
3) Starting at the motor and working out, add symmetrical pieces in a circular formation.
4) NOT IN GUIDE: Add a carnival-like scene below the wheel with LEGOs (optional)
(Final product picture)
Step 3: Programming
The programming is a bit difficult, but any amateur can find a way. The motor directly connected to the NXT is the speed control. It is plugged into port A. The wheel motor is connected to port B.
The coding has to go something like this:
When Motor A is turned X degrees, Motor B spins Y(speed)
It's very easy to figure out, you just need a more advanced knowledge of how the program works. If you make a program you think is easier or better than mine, I would love to here about it in the comments.