Marcia Ascher's introduction to ethnomathematics is probably the best place in which to make one's first acquaintance with the subject. The idea is to study mathematical (or pre-mathematical) aspects of various non-Western cultures.
The idea of ethnomathematics was first articulated in Ethnomathematics, an essay by Ubiratan D'Ambrosio. In his hands, the intention was clearly and unabashedly political: by investigating and valuing the mathematical contribution of other cultures, one could make up for the cultural dominance of "Western" mathematics. Ascher's take on the subject is more descriptive, though she is clearly in sympathy with the political goals as well. She returned to the subject in her Mathematics Elsewhere.
Numbers: words and symbol
Tracing graphs in the sand
The logic of kin relations
Chance and strategy in games and puzzles
The organization and modeling of space
Symmetric strip decorations
In conclusion: Ethnomathematics