There are plenty of essays around on Juvenal's satires, our current read, unfortunately, most of them on JSTOR. A search "Juvenal AND satire" generates a lot of discussion about individual satires.
(If you live in the U.S. and are not affiliated with a university or college, you can ask your public library to subscribe to JSTOR. It's not very expensive, and there is a subscription scale depending on the size of the library. You then can download articles for your own use.)
An accessible online essay is Lessons from Juvenal by Roger Kimball, The New Criterion Vol. 21, No. 8, April 2003.
In print, I found an excellent book of essays in my public library: Essays on Roman Satire (Princeton Series of Collected Essays, 1982) by William S. Anderson. It might be worth a check with your own library. About a third of the book is devoted to Juvenal. The author has studied Juvenal in depth, beginning with his PhD thesis. More on this in another post.
More on Juvenal can be found at About.com: Latin Poetry - Juvenal Roman Satirist.