Make:

Another quick & easy option for those getting started with the popular micro - Little-Scale posted a quick rundown on using a solar cell for Arduino sensory applications.

• The solar panel used in this example was rated at 2V and 25mA.
  
• Do not use a solar panel rated in excess of 5V. Doing so may damage the Arduino
  
• If data values appear incorrect, try scaling the byte 'data' in the Arduino sketch as it is captured.
  
• The analog inputs read data at 10 bit. However, a single, serially-printed value can only hold 8 bits of information.
  
• The data range with this particular solar panel is 0 < 6 using power-efficient, indoor lighting at night

In the Maker store:

Solarbotics Solarcell_B