Many of us spend a lot of time commuting. What better way to pass the time than listen to some great teaching, or discussions on matters related to Christian truth. There is a wealth of free audio resources on the web from top-notch thinkers that will help think more clearly about issues of truth. Here are some I would recommend:

Stand to Reason radio
Stand to Reason podcasts
William Lane Craig

Converse With Scholars
Southern Bapist Theological Seminary lecture series

Veritas Forum

I guarantee that your mind will be stimulated, or your money back!