NerdKits - DIY Marquee LED Array Display
http://www.nerdkits.com/videos/ledarray2/

double your addressable LEDs

The Teensy is a complete USB-based microcontoller development system, featuring a 16 MHz AVR (AT90USB162) processor, in a very small footprint! All programming is done via the USB port. No special programmer is needed, only a standard "Mini-B" USB cable and a PC or Macintosh with a USB port.

Cheap Arduino wireless communications

I was looking for a way to handle wireless communications between two Arduino boards. Other options like Xbee or Bluetooth were going to cost $50 to over $100. Then I found a cheap RF transmitter and receiver at Sparkfun. The total cost is only $9!