This is one of my favourite photos, of a cap cloud over Ball's Pyramid, New South Wales :
It would be interesting to know what atmospheric conditions had been present that day, & whether this is a common phenomenon. As I mentioned before, I like cap clouds a lot and this must be the Mother of all Cap Clouds.
The other photo I really like is this one of a cumulonimbus, over Point Lookout, also in New South Wales :
I've seen a lot of cb clouds since then, but somehow nothing can beat this one. It looks quite unique. In fact I once showed it to a group of air traffic control students and they couldn't even recognise it as a cloud. One student asked if it was real or a painting.
The photos are from the 1994 Australian Weather Calendar which a friend of my mother's is kind enough to send me every year. I've had these on my locker for over 10 years & they've become quite faded. Even so, I haven't found any others I like enough to replace them with, despite the fact that subsequent calendars have had some pretty spectacular photos.
and have a look at some other weather calendars as well.