Here is a short list of writings by Pope Benedict XVI before being elevated to the papacy.
I'd like to add a couple that have been instrumental in shaping my understanding of his views:
The Ratzinger Report (Ignatius Press)
Daughter Zion (Ignatius Press) out of print
For many more, try a Ratzinger search at the Ignatius Press website.
I'm sure all his prior writings will be closely scrutinized for his opinions on various issues.

Nice move in Spain. We can only hope your new NAZI POPE dies quickly
of another brain hemorrhage. //
Epithets of ignorance...truly, nothing is new under the sun.
The Chicago Tribune reports that Pope Benedict XVI's books are selling like hot cakes: "Six of Amazon.com's top 25 sellers on Friday were books by Ratzinger, with his 'Introduction to Christianity' ranking the highest, in the 11th spot. Another sought-after book is his memoir, 'Milestones,' in which he talks about his childhood under Nazi oppression."
This CNS article lists many of the pope's principal public documents, written before he becaome pope. There are no accompanying links to web addresses, but I think the list is valuable nonetheless.
"Don Capisco" provides "a brief bibliography" of "Joseph Ratzinger on The Theology of Worship and of its Music" here.