You can get some cool stuff for cheap on dx.com. For example this TM1638 display board costs around $8 and has eight 7-segment digits, eight two-color LEDs and eight buttons. I connected it to a Raspberry Pi and made a Bitcoin price ticker:
Even though I didn't get any documentation with the board, the protocol it uses is well known on the Internet, I found this Arduino library and ported the parts I needed to Python to run on the Pi. You need three GPIO pins on the Pi to connect to DIO, CLK and STB0 pins on the board. You also need to connect the VCC pin on the board to the 5V pin on the Pi and GND to any of the grounds.
Getting a price to display is easy, Bitcoin exchanges usually provide this data via a JSON service. You can see my code here.
Like I mentioned before, the display board also has buttons, so it would be nice to extend this to display prices from multiple exchanges, using the buttons to select which price you want to see.