Philippians Resources
Commentaries

The Letters to Philippians, Colossians, Thessalonians by William Barclay
The Letter to the Philippians by Walter G. Hansen in The Pillar New Testament Commentary series
Philippians by Moises Silva in the Baker Exegetical Commentary Series
Philippians by John MacArthur in The MacArthur New Testament Commentary series
Philippians:  An Introduction and Commentary by Ralph P. Martin in the Tyndale New Testament Commentary series

 
Online Resources

Introduction to Philippians by The Gospel Coalition
This site contains information on the book of Philippians such as Author & Date, Genre & Setting, Themes & Background, Outline, Scripture, Teaching & Preaching, and Recommended Resources.
Look at the Book by Desiring God with John Piper