Other types of clouds:
Mammatus clouds are dark clouds shaped like sagging pouches. These clouds often appear after a tornado.
Orographic clouds are clouds that are formed as moist air rises over mountains or other major geographic features. The air floats up the side of the mountain and cools quickly, condensing and turning into a cloud.
A pileus cloud is a smooth cloud that is found over or on the top of a major geographic feature, like a mountain.