I stumbled upon a very cool site this morning from the UK called Atmospheric Optics. The site is comprised of an extensive series of images and explanations (some of the best I have ever seen) for the most common optical phenomena that result from various atmospheric conditions.
Rainbows, halos, shadows, ice crystals, and sunsets all figure prominently. Do check it out if you have even a passing interest in physics or even if you just like pretty sunsets. Here’s a sample on the directory page for the Rainbow Section.