There's not much I can add to this other than how much I loved how Wayne Grudem put it in his book Systematic Theology. He lists the purpose of the Church in three catagories. Here it goes....
1. Ministry to God: Worship. In relationship to God the church's purpose is to worship Him. Paul directs the church at Colossae to "sing psalms and hymns and spiritual songs with thankfulness in your hearts to God" (Col. 3:16). God has destined us and appointed us in Christ "to live for the praise of his glory" (Eph. 1:12). Worship in the church is not merely a preparation for something else: it is in itself fulfilling the major purpose of the church with reference to its Lord.
2. Ministry to Believers: Nurture. According to Scripture, the church has an obligation to nurture those who are already believers and build them up to maturity in the faith. Paul said that his own goal was not simply to bring people to initial saving faith but to "present every man mature in Christ" (Col. 1:28). And he told the church at Ephesus that God gave the church gifted persons "to equip the saints for the work of ministry, for building up the body of Christ, until we all attain to the unity of the faith and of the knowledge of the Son of God, to mature manhood, to the measure of the stature of the fullness of Christ" (Eph. 4:12-13). It is clearly contrary to the New Testament pattern to think that our only goal with people is to bring them to initial saving faith. Our goal as a church must be to present to God every Christian "mature in Christ" (Col. 1:28).
^ I love this, because so very often we lose sight of what were suppose to be doing....strengthening, encouraging, and building up Christians and equipping them to do the will of God. There is always more to learn about God and His Word.
3. Ministry to the World: Evangelism and Mercy. Jesus told his disciples that they should "make disciples of all nations" (Matt. 28:19). This evangelistic work of declaring the gospel is the primary ministry that the church has toward the world. Yet accompanying the work of evangelism is also a ministry of mercy, a ministry that includes caring for the poor and needy in the name of the Lord. Although the emphasis of the New Testament is on giving material help to those who are part of the church (Acts 11:29; 2 Cor. 8:4; 1 John 3:17), there is still an affirmation that it is right to help unbelievers even if they do not respond with gratitude or acceptance of the gospel message.
^ Jesus last command was His greatest, make disciples. There are so many opportunities in our everyday life and so many ways to witness, its exciting! I know whenever I think about this I also think of the day when we see Christ and I know that my work will not have been in vain. How much it will mean to hear Him say "well done" or "good job, my faithful servant".
Grudem goes on to say alot more but this is what spoke to me today. He lists first the greatest, ministry to God. After worshiping God comes ministry to believers and nurturing others. Then after that and believers are being nurtured, you minister to unbelievers helping them and sharing what God has done. All three of these ministries goes hand-in-hand, you cannot have one without the others. Very often churches place priority on one the purposes over the other three. Grudem says "all three purposes must be emphasized continually in a healthy church".
So to sum it up,
-Love God and give Him all the praise
-Strengthen other Christians
-Share God's love with unbelievers