I really like the idea behind NSKyC, where a webcam image is taken every five minutes and then the average sky color is calculated and converted to HEX. The result is then displayed in large format on the single-serving site.
What you get is a surprisingly accurate overview of the weather in NYC from a very high level. Scrolling down, you can see cloudier parts of the day, sunrise and sunset, and bright, sunny stretches. Rolling over any five minute period shows you the webcam screenshot used for the calculation.