This kit looks pretty easy to use, just send the line to be displayed over a COM port. It even supports hex letters (a,b,c,d,e,f) – of course, a 14-segment version would be even cooler. Still, a lot of potential applications – USB7

U-Disp – An open source USB display
Seven-segment big LED display

In the Maker Shed:
Led Microreaderboard Kit Crop
LED Micro-Readerboard Kit