Ach! ES beat me to it with the fogbow pic. I was looking back through the archive 'cause I remembered having seen it recently, only to find it'd already been posted. Oh well, here's another sun pillar like the ones in the op:
(also from APOD, btw).
Of course, then there's also lenticular clouds:
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One interesting thing about lenticular clouds is that they stay in the same place over the ground, even when a strong wind is blowing! The air has to be stable and flowing in a smooth laminar manner without much vertical mixing for these clouds to form.
When the wind is deflected upwards by a mountain range, or sometimes by a weather front, standing waves form in the air downwind of the obstruction. It's a bit like the 'stationary' ripples you sometimes see in a river, downstream of a rock - but because the air is an elastic medium the waves are much higher than the mountains that form them - sometimes up to ten times higher.
If the air is moist then droplets of water condense as the air rises and cools, then the drops evaporate again as the air falls and warms - so the clouds sit on the top of the atmospheric waves. The wind is blowing straight through the clouds at perhaps 50mph or more - the cloud is constantly forming at the leading edge and evaporating at the trailing one. As long as the wind conditions remain constant, then the waves stay in the same place relative to the mountains that formed them - hence the 'standing cloud' effect.
Glider pilots who are aiming to fly high love these wave conditions - I've soared in gliders along the edges of these clouds, sometimes with one wing slicing through cloud and the other out in bright sunlight! Up close they look magnificent.
Glider pilots have soared to over 40,000 feet using this wave lift! I've never been that high though - even in the fifteen to twenty thousand feet height range we are able to reliably reach here in the UK (with our relatively small mountains), it's bloody cold, and you have to take bottles of oxygen with you! At over 40,000 feet, breathing pure oxygen isn't sufficient - you really need a pressure suit if you want to avoid injury and/or death.
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This striking aurora image was taken during a geomagnetic storm that was most likely caused by a coronal mass ejection from the Sun on May 24, 2010. The ISS was located over the Southern Indian Ocean at an altitude of 350 kilometers (220 miles), with the astronaut observer most likely looking towards Antarctica (not visible) and the South Pole.
The aurora has a sinuous ribbon shape that separates into discrete spots near the lower right corner of the image. While the dominant coloration of the aurora is green, there are faint suggestions of red left of image center. Dense cloud cover is dimly visible below the aurora. The curvature of the Earth’s horizon (the limb) is clearly visible, as is the faint blue line of the upper atmosphere directly above it (at image top center). Several stars appear as bright pinpoints against the blackness of space at image top right.
Hovering in the sky, this rainbow cloud over Mount Everest took an astonished astronomer by surprise. Oleg Bartunov, 51, caught the spectacle on camera during a Himalayas expedition in Nepal. [840x962] (i.imgur.com)
Caption is copy-pasted directly from reddit. I have no idea about its veracity.
It looks legit (or at least, possible) to me. Cirrus clouds have been known to contain rainbow colors in the form of a halo, if their position with respect to the sun is right. Usually this creates more regular arcs, like the more familiar rainbow in liquid water droplets; I suppose the swirling colors in this picture may be due to the cloud having a wave-like shape, which isn't all that crazy near a big mountain range like the Himalayas.
It's a beautiful picture in any case.
ETA: This page has some more information on this kind of phenomenon. Eyeballing it, I'd say we have a particularly stunning iridescent cloud on our hands.
ETA2: Or perhaps a nacreous cloud. Sheesh, you'd think that after a couple of years of working on the radiative transfer of solar radiation by clouds I'd know this shit. Apparently not.
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Last edited by Pan Narrans; 10-13-2011 at 05:04 PM.
Oh, I didn't doubt the authenticity of the photo, I just have no idea whether the circumstances in the caption are real. Still, awesome picture no matter what.
An Iridescent Cloud in Himalaya, I observed early morning on October 18, 2009 from path to Khumjung, just 500 meters from road fork to Gokyo and Tengboche. I was ahead of my friends, so when I met my Annapurna buddy, who was going to Khunjung (to see Yeti scalp) I decided to go with him for a while. We sat on stones to talk and drink my green tea and suddenly I saw this spectacular phenomena . It was my first time I saw this phenomena and luckily I had my Nikon D90, so I was able to capture it. I called other people's attention (english wimin) to this, but not sure if they succeeded to capture it with their soap-camera. I was lucky also, because my friends didn't see anything. Turbulence, ice crystals in the low cloud and wonderful Himalaya produce this great picture. The mountain is Thamserku (6623 m).
After saying in the OP that sundogs are more common than rainbows, I've been keeping a look out for them!
Okay, I'm outside more on showery days (good for rainbows) than I am just after sunrise on cold sunny mornings (good for sundogs) but I'm going to admit that my OP claim was wrong (for the UK anyway) as I'd not seen a good sundog since the OP until this week.
But on Tuesday morning, driving down the M40 to London at about 6:45 am, there was a beauty! Only on one side of the sun, but it was really clear. I didn't risk trying to photograph it while I was driving though, and by the time I got to the motorway service station where I could stop, it had gone.
This is known as a Fallstreak Hole. The one in the photo was snapped over Korumburra in Australia. It occurs when a cloud has supercooled below freezing: initially the cloud is unable to freeze into ice crystals as the water is too pure and lacks the microscopic bits of salt or similar to act as seeds for the ice. When some crystals do eventually form near the centre of a cloud then a domino effect can occur leading to the sudden appearance of the hole.
There was a rainbow outside my work a couple days ago. Just a regular rainbow, not double or anything, but it was huge and solid(-looking) and stretched from horizon to horizon. It was just kind of cool in the middle of the work day having people randomly get up and go to the window and go "ooh! rainbow!" and enjoy a bit of beauty.
Re: Atmospheric optical phenomena
Sonoma Bear
Only on one side of the sun, but it was really clear. I didn't risk trying to photograph it while I was driving though, and by the time I got to the motorway service station where I could stop, it had gone. 
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