… that deal, directly or indirectly, with how language and culture/thought processes interact, all these books are well worth reading:
Language and Art in the Navajo Universe, by Gary Witherspoon
Flutes of Fire: Essays on California Indian Languages, by Leanne Hinton
American Indian Languages: Social and Cultural Contexts,by Shirley Silver and Wick R Miller
And for those who are really hardcore into linguistics and want something to get your teeth into:
The Languages of Native North America, by Marianne Mithun