Make a scrolling sign, or a small video display with this 8x8 gridded bi-color LED matrix. Only 1.2" on a side, it is quite visible but not so large it wont plug into a breadboard! 128 LEDs are contained in the plastic body, 64 red 320mcd and 64 green, in an 8x8 matrix. Every grid has two LEDs inside so you can have it display red, green, yellow or with fast multiplexing any color in between. This display is bright, beautiful and funky with nice diffused square lenses for a striking look. There are 24 pins on the side, 12 on each, with 0.1" spacing so you can easily plug it into a breadboard with one row on each side for wiring it up.
Since the display is in a grid, you'll need to 1:8 multiplex control it. Adafruit suggest either using two 74HC595s and TPIC6B595 (using the 74HC' to control the 16 anodes at once and then using the TPIC' to drive one cathode at a time) or using two MAX7219 which will do the multiplexing work for you.
The Arduino playground has a nice set of tutorials introducing the MAX7219 and 8x8 LED matrices