For those of you with a biological bent and have an interest in generating different types of algae, the following project should be of interest. Jared Bouck has documented not only the electronics side using an Arduino board but the construction details for the bioreactor as well.
According to Jared
each algae species reacts differently in many ways to its environment and a light frequency that affects one algae may have no effect at all on another. So I have created an easy to build microcontroller platform that can be variably set and allows for easy configuration to any bioreactor. The LEDS can be swapped out to experiment with different colors and even UV for some hydrogen producing species. The platform is flexible enough to add other features like relay control for lighting, pumps, agitation and cooling and heating. While you may not be an algae fan like I am there is tremendous potential in this simple organism ...
If you're looking to make your own projects that could use different light effects, consider the Freetronics RGBLED: module. It includes a bright RGB LED on the top of the board and a WS2801 constant-current, addressable, multi-channel LED driver on the back. This smart module can be daisy-chained, so you can connect a number of these together in a string and drive each of the module colours individually from your microcontroller. For more information and to order, visit the product page.