This is not as much an instructable as a record of how I made a school project. While repeating exactly what I did will probably not help you, this project can be modified to make almost any display more eye-catching.
Step 1: Come Up With an Idea
I know this sounds stupid but it is necessary to know at least roughly what you are trying to do. In this case, I wanted to somehow incorporate astronomy and draw attention to my poster. With this in mind, I came up with a cheesy saying and a plan for the placement and animation of the LEDs.
Step 2: Generate a Poster Design
The next step is to create a conventional poster, either by writing/drawing it out on paper or posterboard or by using a program such as Jasc Paint Shop Pro or Adobe Photoshop. Be sure to do a good job here as a great electronics display can only help a crappy poster so much.
Step 3: Gather Tools and Materials
Now the fun begins.
You will need:
-Some sort of marker or sharpie
-A straight edge
-Tape (scotch or other clear variety)
-Needle nose pliers
-Electrical tape or heat-shrink tubing
-A backer for the poster (I used masonite but stiff cardboard or sheet PVC should work)
-Sandpaper (medium grit)
-A power source
-A breadboard to test it all
...and a partridge in a pear tree.
Don't worry, it sounds like more than it actually is.
Step 4: Make Backer
While you probably have a very beautiful poster at this point it is not nearly thick enough to support the electronics. Using the straight edge, mark a piece of the backer board the same size as the poster and cut it out.
Step 5: Sand Down the Edges
When you cut the masonite it will probably have rough edges. Five minutes with a piece of sandpaper can go a long way towards making your display look nice.
Step 6: Program the Microcontroller
Now it's time to program the microcontroller. Since I am new to microcontrollers and don't own a "real" one such as an Atmel AVR or a PIC microcontroller, I used a clunky version of the Parallax BASIC Stamp called a "Homework Board." It came in a kit called "What's a Microcontroller?" but it was easy to program, it met my needs and I had it on hand. My program was very simple but got the job done, lighting up the LEDs in the correct order at a reasonable brightness with no extra chips.
Step 7: Place the LEDs
Now it's time to place the LEDs. If you want to be extra careful and have the LEDs placed extremely accurately you can drill holes for the leads, but if you're using masonite you can just poke holes through the backer board with a resistor's leads. If the holes aren't perfect it's not a big deal, just make sure that you have a separate hole for each lead so that they don't short out.
At this point you may also want to attach your microcontroller to the back, preferably in an out of the way location such as a corner. Since I was worried about the weight of my micontroller being an issue, I ran a wire through the holes in the board, through some holes in the masonite that I drilled, and back to the beginning where I soldered it to itself. I didn't get a good picture of this, but it's probably just as well as it was overkill and tape would probably work better anyways.
Step 8: Solder Together the Electronics
Now it's time to solder. Since the leads will probably cross, be sure to insulate them to prevent a short circut. Also, if the electronics look like crap (like mine do) then don't worry, people won't see it (unless you show them). Just be careful not to burn yourself or start a fire.
Step 9: Show Off Your Project
Congratulations, you now have a very eye-catching display. Set it up in a hallway or at a convention and watch as people walk over to look at it.
I hope you've enjoyed this instructable. Please comment as it is my first instructable and any feedback will help me make my next one better. Thanks for reading!