Alex Schlegel built this most excellent day table. Besides being just a pretty table, it has a set of LEDS and a sensor embedded in it, and it displays the current and past light on them:
The Day Table table acts as a record of the previous day by sensing ambient light levels in its environment and displaying them through 24 LED strips embedded just below its surface. The rightmost LEDs show the most recent light levels and the leftmost show the light levels of a day ago. Day and night transitions can be seen, as well as human activity through actions such as turning lights on and off in the room where the table resides.
Source code and build plans are available at his site.Related