Here is a list of projects that you can do with an Arduino that are ... than just connecting sensors, but still very easy for ...

Calibrating the system using a bowl of clean water. There is no single parameter that determines the quality of a water sample, so the pollution monitor has no less than five different sensors.

Note: This appears to have changed from the 1.60 to the 1.6.5 version ... how sensors are reacting to the environment. I’ve switched completely to using Eclipse for my Arduino projects.