Phooky from NYC Resistor wrote about his hackerspace’s LED sign:
It’s Hexascroller, your friendly neighborhood integrated clock/wireless notification system/annoying beep generation solution! Hexascroller was hacked together from donated LED panels for this past spring’s Interactive Party. It’s got six 30×7 LED displays, an Arduino Mega, a charmingly obnoxious loudspeaker, a DS1307+ RTC, and an XBee all hanging precariously from a wooden frame assembled with sturdy hot glue construction techniques. It’s hanging from a ceiling beam in our front room like some demented Flying Saucer of Damocles.
At the Interactive Party we had Hexascroller displaying tweets, but nowadays it primarily functions as a clock. You can use an XBee to connect to it if you need to scroll a message or make a horrible noise to draw attention to the message you’ve just scrolled.