Here are some great articles for Lesson # 31 in Gospel Principles on Honesty to use as reference. Remember that its all about personal revelation when you are compiling your lesson. I hope these help some.
"Honesty, A Principle of Salvation" by Elder Mark E. Petersen - Talks about hypocrisy, dishonesty, and deception. "But in our society is there anything more widespread than the tendency to lie and deceive?" written in 1971
Ethics and Honesty by Elder David B. Haight- includes talk on how the USA and thus the gospel could not have happened with this good quality trait and how we are loosing it.
"Honesty-a Moral Compass" by Elder James E. Faust- Given in a Priesthood session. Great description on what honesty is.
"There is No Harm" by Elder Marvin J. Ashton- Discusses what lying is and the results.
"We Believe in Being Honest" by President Gordon B. Hinckley- an ordinary subject but the very essence of the gospel.
"Basics Concepts of Honesty" by Elder Howard W. Hunter- the foundation of character.
"Honestly, There's No Better Way" by Brad Wilcox- has tips for parents on how to teach honesty.
"Teaching Children to Be Honest" in the Ensign 1985 tips to teach children.
"The Eternal Importance of Honesty" by Elder Richard J. Maynes- "Our eternal life depends on the principle of honesty."
Please remember the church's guidelines when using articles in your lessons.