An early edition of Smyth's Classical Greek grammar as well as an overview of Greek Grammar keyed to Smyth are available online through the Perseus project. John Gruber-Miller has added a review of Ancient Greek. You may also purchase a print copy of the most recent edition of Smyth's grammar from Amazon.com.
This grammar assumes a certain amount of knowledge of Classical Greek, but it has remained the standard for studies of Biblical Greek for several generations.
•Moulton-Howard-Turner, Grammar of New Testament Greek
The first two volumes of this four-volume work are particularly valuable.
Volume three is heavily dependent on the much earlier work of Edwin Mayser in German. I do not recommend it, but if you want the complete set you may order it here.
This enormous volume from the early twentieth century provides a wealth of examples and is in part an evaluation of and reaction to the work of earlier scholars. It's treatment of Case is not widely accepted.
This is a treatment of the syntax of the the Greek found in the New Testament with a strong focus on the exegetical significance of the grammatical principles discussed.