As one of his first Arduino-based projects, James Wynne organised the typical Arduino and Ethernet shield combination and created the webserver example. Further on from this he added a temperature and humidity sensor module and can now monitor the values returned from the sensor using the webserver. Although it's quite simple, projects like this form a great base for more complex or interesting examples and are a good learning experience. In the following example James explains it in more detail:
If you're looking for a sensor to measure temperature and humidity - check out our HUMID: humidity and temperature sensor module. Designed around the DHT22 sensor, it only requires one digital pin and power - and is easy to use with out Quick Start guide. With a temperature range of -4°C to +125°C with +/-0.5°C accuracy, and humidity at 0-100% with 2-5% accuracy you're ready to measure. For more information and to order, click here.