Nijay Gupta shares his final post in this helpful series on best commentaries by listing two essential works on Philemon.
Here I will comment briefly on Philemon.
For an excellent, up-to-date technical commentary, check out Scot McKnight (NICNT).
For more basic treatments, look at the following:
The T & T Clark Study Guides volume on Colossians and Philemon by John M. G. Barclay.
Be sure to bookmark the complete series on Paul, only on the Academic Blog.