Most well-known literature on simple-system flutes is dominated by the concert flute and the Irish flute, with brief mention of pennywhistles and the military fife and drum corps in the US and Britain. However, very similar instruments are played in other musical traditions, less well publicized. Here are the ones I've found out about. Please tell me if you know of others.
The southern black fife and drum tradition:
The South African Kwela pennywhistle tradition:
Wooden flutes used in traditional music from Galicia (Spain), called a requinta. Traditionally pitched around F, i.e. somewhat smaller than an Irish flute.
The northern European overtone flutes. These have no holes at all and are played entirely by overblowing.
Apparently Southern Africa has a similar instrument, called the Lekgodilo flute. Youtube video