Jailbreaker's post below highlights a common fallacy rampant in the church: The church building as the "house of God".
In Old Testament Israel, the answer to the question seemed quite simple--the temple in Jerusalem was the house of the LORD, though the LORD Himself expressed some ambivalence over the designation: "Heaven is my throne, and the earth is my footstool. Where is the house you will build for me? Where will my resting place be?" Still, the temple was where God officially met with His chosen people, and it was referred to as His house. Even Jesus defended it as such: "How dare you turn my Father's house into a market!"
But Jesus also came to usher in a new covenant, announcing that the time for worship in Jerusalem was ending ... the time for worship "in spirit and in truth" had arrived. God's temple is now in His people, both individually ("your body is a temple of the Holy Spirit") and corporately ("we are the temple of the Living God").
This is no small point, and reveals a downside of church organization, and a trap into which we all fall--the tendancy to value to the physical over the spiritual. A church building may be a useful thing, but it is only that. Sadly, it very easily becomes the center of our corporate existance, and too easily displaces the true house of God (and perhaps even God Himself) in our hearts.
Next time you hear someone refer to the church building as the house of God, gently remind them that it is not the building, but we ourselves "like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ."