Just read through this story from NPR and thought it is fantastic. Every parent should read it. It's a little long but well worth the read.
The author reviews studies about children and lying and gives some great advice about how and why it happens and how to deal with it as a parent.
If you are like me, you'll find that you are still doing lots of things that are encouraging lying. I was aware of the many ways that children consider that parents are lying - my children have called me on them - and I work hard to avoid lying to my children for any reason. Sometimes the way to avoid it is to be purposely vague when they ask for a promise of doing something in the future. Unless I'm absolutely certain I can do what they are asking, I usually just say, "Maybe. Sometime".
I know I have been frustrated at times by my inability to know whether or not my children are telling the truth. The article really gives me some tools to monitor my own behavior so that I am encouraging my children to be honest.