The Gospel According to Luke I-IX: Introduction, Translation, and Notes (The Anchor Bible, Vol. 28) A thorough and comprehensive commentary for which some knowledge of Greek would be helpful. (Also see the second volume.)
The Gospel According to Luke X-XXIV: Introduction, Translation, and Notes (The Anchor Bible, Vol 28A) (Chapters 10-24 v. 2) A thorough and comprehensive commentary for which some knowledge of Greek would be helpful. (Also see the first volume.)
Augsburg Commentary on the New Testament: Luke Knowledgeable yet accessible
Sacra Pagina: The Gospel of Luke One of the better newer commentaries on Luke
The New Interpreter's Bible: Luke - John (Volume 9)
The Gospel of Luke (The New International Commentary on the New Testament)
The Theology of the Gospel of Luke (New Testament Theology) Not a commentary but a helpful theological overview
Reading Luke: A Literary and Theological Commentary on the Third Gospel (Reading the New Testament) (Volume 3) Provides a bigger picture view of Luke highlighting literary and theological themes
Social Science Commentary on the Synoptic Gospels Very helpful resource for Synoptics; Organized by book:chapter:verse, it highlights significant social and cultural issues and points to longer articles at end
New Proclamation: Year C, 2009-2010, Advent Through Holy Week
Manga Messiah This is a life of Jesus drawn from all four Gospels; Luke's account has a prominent role; distinctive and interesting presentation!