I build a coffee table with RGB LEDs, as you can see in the following youtube video:
For this project I first bought a cheap IKEA table for 5€ and cut a square hole in it.
In this hole I glued walls out of white styrofoam with this 5 x 5 squares as you can see in this picture:
The LEDs are 25 12mm diffused RGB LEDs with a 5V WS2801 Drivers for the SPI interface of the raspberry pi.
I put the pi in one of the walls of the table and closed the table with a mat transparent plexiglass.
The last thing I have done was assembling two arcade buttons on the sides of the table to control different games with them.
The programming is done in python. You can find the code on github: https://github.com/stetro/pix-table
I hope you like it, and if you have any question, you can always ask me ;-)
There is also a german blogpost about this project: http://stetro.wordpress.com/2013/02/28/led-coffee-table-raspberry-pi/