Even a cursory reading of the prophets will convince you that idolatry is one of the main objects of God's displeasure. "Do not go after other gods to serve and worship them, or provoke Me to anger with the work of your hands" (Jeremiah 25:6). But is idolatry limited to making some sort of pagan figurine and then prostrating before it?
Idols can be anything that we substitute, in some sense, for God. It's not only a matter of worshiping them, but simply of serving them. It may be that we don't explicitly think of money, prestige, possessions, sex, pleasure, etc as "gods," but when we see the disproportionate amount of time and energy we invest in them (compared to what we give the true God), then we must ask ourselves: whom do we really serve? You don't need to go to some pagan temple to commit idolatry. All you need to do burn the incense of attention over the dark flame of passion--of whatever sort: greed, lust, ego-building--and you are serving an idol. These idols will eventually fail us, for they are not of God. Then what shall we do? "They have turned their backs to Me and not their faces. But in time of their trouble they say, 'Arise and save us!' But where are your gods that you made for yourselves? Let them arise, if they can save you..." (Jeremiah 2:27-28).
Jesus doesn't say too much about idols, but He does speak of other masters, which is the same thing. "No one can serve two masters... You cannot serve God and mammon" (Matthew 6:24). "Mammon" means not only money but anything in which you put your trust. To serve anything other than God is to serve another master, an idol. There are many different kinds of service we are required to perform, and not all are explict acts of worship. But if whatever we do is good in itself, it can be offered as service to God. Any sinful acts, however, constitute service of an idol, and behind every idol stands a demon.
So when we examine our lives we should notice where our time and energy go, that is, which master we serve. What is the desire of our hearts, what moves us most powerfully, what is most important to us in life? "Children, keep yourselves from idols" (1John 5:21), so that you may serve "our only Master and Lord, Jesus Christ" (Jude 4).