As a third grade teacher, I try to encourage students to read from a variety of genres in order to comply with the California Language Arts Standard of reading and responding to a variety of literature.  Although there are many different types of nonfiction genres out there, these are the main categories I address with my third graders at school.  The fiction genres are addressed in 3 other hubs, "Childrens Literature - Fiction Genres" Parts 1-3.

A true life adventure that really happened
Example:  Incredible Animal Adventures by Jean Craighead George

A true story of the author's life written by the author
Example:  Boy by Roald Dahl

A true story of a person's life written by another person
Example:  Meet Martin Luther King, Jr. by James T. deKay

A true story about the life of previous time periods, or a true account of a past event or time period
Example:  If You Traveled West in a Covered Wagon by Ellen Levine

A true account of scientific discoveries, inventions, and/or information
Example:  Stars and Planets by Ian Ridpath

An account of facts about sports
Example:  Soccer by Gary Lineker