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.