I just came across this quote which a friend of mine posted on his blog. I don't really know anything about the author but the quote is great...
From Tim Keller’s new book, Counterfeit Gods:
What is an idol? It is anything more important to you than God, anything that absorbs your heart and imagination more than God, anything you seek to give you what God could only give.
A counterfeit God is anything so central and essential to your life that, should you lose it, your life would feel hardly worth living. An idol has such a controlling position in your heart that you can spend most of your passion and energy, your emotional and financial resources, on it without a second thought.
It can be family and children, or career and making money, or achievement and critical acclaim, or saving “face” and social standing. It can be a romantic relationship, peer approval, competence and skill, secure and comfortable circumstances, your beauty or your brains, a great political or social cause, your morality and virtue, or even success in Christian ministry. When your meaning in life is to fix someone else’s life, we may call it “co-dependency” but it is really idolatry.
An idol is whatever you look at and say, in your heart of hearts, “If I have that, then I’ll feel my life has meaning, then I’ll know I have value, then I’ll feel significant and secure.” There are many ways to describe that kind of relationship to something, but perhaps the best one is worship.