American Ways by 
Becoming a U. S. Citizen by 
Living in the U.S.A by 
Voices of Freedom: English and Civics for U.S. Citizenship by 
American Ways by 
Pass the U. S. Citizenship Exam, Fourth Edition by U.S. Citizenship and Immigration Services - Lots of information and forms.
U.S. Citizenship and Immigration Services: Study Materials for the Naturalization Test - Free materials to prepare for the Civics test as well as the English test.
Learn About the United States: Quick Civics Lessons for the Naturalization Test - 36 page brochure from theOffice of Citizenship explaining the answers to typical questions from the naturalization test.
U.S. Citizenship Exam Preparation - Timberland Regional Library system subcribes to the online Learning Express Library, which has exam preparation in English and in Spanish. You will need a Timberland card to access this from home.
U.S. Citizenship Test Review
The Story of America