Some more quickies:
I found a really great resource for skies and atmospheric references, the photo gallery at AccuWeather.com
While I usually search for reference on google image, this site has thousands of user uploaded photos of clouds in all kinds of situations, they can be filtered out by tags which makes it very convenient to pin down specific weather and time-of-day conditions.
Great clouds, especially the quick ones on the bottom!
SvaraRadera