Second Corinthians 5:6-8 makes it clear that the believer is ushered directly into the presence of God upon death. Paul argues that "to be absent from the body" is tantamount to being "present with the Lord." Jesus sounded a similar theme when He told the thief on the cross "today you will be with Me in Paradise" (Luke 23:43). The paradise Jesus referred to is synonymous with heaven.
However, Scripture also teaches that the believer, while in the presence of the Lord, will not receive his glorified body until a later time. Upon death, our bodies go into the grave and await the second coming of Christ (1 Thess. 4:16), when He will raise and transform them (1 John 3:2).
The apostle Paul speaks of the time when our spirits will be again united with our bodies so that we will no longer be naked (2 Cor. 5:3) but able to live throughout eternity in the form God created us to enjoy. The new body of the Christian is yet future, though each deceased saint is now in the presence of the Lord.
For more information on heaven, take a look at John's book, The Glory of Heaven.