Cinnamon is typically found in long sticks, which are formed from peeled and dried bark. Cassia is a commonly found cinnamon replacement, and in many cases anything labeled simply as "cinnamon" is actually cassia.

The following recipes on this site use cinnamon:

Hot Buttered Rum (batter mix)
brown sugar, butter, salt, nutmeg, cloves, cinnamon,
Tom and Jerry (batter mix)
eggs, rum, cinnamon, cloves, allspice, cream of tartar, sugar,