I was sent this photo from a mobile phone yesterday - hence the not completely wonderful quality!
A little cloud-watching is something I have a lot of time for. I plucked a cloud book from my shelf (everyone should have a cloud book! I have two . . . ) and discovered that my vague hunch was right, and this cloud is called Altocumulus Lenticularis. Okay, I only got the lenticular bit from memory. Unsurprisingly, it's often mistaken for being a UFO.