I was in college when I had my strongest experiences forming an individual relationship with the Church and forging much of what is my own testimony. I served a mission and had some great experiences, but it was at college that I learned the most about my own perspective - my own personal faith.
I took a number of classes at the Harvard Divinity School, and I was deeply impressed by a few things:
1) "Fundamentals of Christian Theology" just didn't resonate with me - AT ALL. The class was taught by a renowned Catholic theologian, and he did a wonderful job teaching the "fundamentals" of mainstream Christianity (and was an excellent teacher). I loved him and his class, but the actual "fundamentals" themselves did absolutely nothing for me. There were so many "Seriously?!" moments, and it really crystalized in my own mind the difference between what I had come to understand and love as "pure Mormonism" and what these brilliant, dedicated, faithful Christians (whom I respected, admired and loved) believed and taught. It was a real Zen slap for me, if I can mix metaphors.
2) I took a class called "Jesus and the Moral Life" from Harvey Cox - the author of "The Secular City" and one of the icons of liberation theology. In that class, I read a couple of books that had a profound effect on me (particularly "Jesus, before Christianity" by Albert Nolan) - ironically, by re-enforcing the distinction I saw between the Gospel, the Church and church culture.
3) I had a couple of Master's level seminars that were small group discussions, with lots of one-on-one interaction with faculty and Doctoral candidates, that were real eye-openers - introductions to not only "mainstream Christianity" but also lots of movements within "fringe Christianity" (like gay theology and feminist theology). Again, ironically, I had a vision of how the core of these fringe theologies actually could fit into pure Mormonism that was amazing.
It was the "meta-level vision", if you will, that was strengthened in these classes and gave me "outside confirmation" of my own testimony.