I understand that Martin Luther believed in the redemption of the will to serve God as part of God's redemptive work. Can someone clarify how this differed from Erasmus' viewpoint? I know I could figure this out through self-research, but I'm looking for an abridged version.
I don't know how abridged a version can be, since it is a very subtle topic. If you really want to understand it in depth, I recommend "Luther: Right or Wrong" by Harry J. McSorley; I consider it one of the best works in the English language on this topic and soteriology in general. This was a topic that affected me greatly in college and reading this book really revolutionized my understanding of justification and salvation, so I really recommend it. If you want a couple-page overview of the debate, here is a link that provides a lot of the context.
If you want a summary that is so general that people will take immediate exception to it (alas), Erasmus believed that free will played more of a role in salvation than did Luther; Erasmus said free will and God's will played a synergistic role and Luther totally rejected that and said our will is in complete bondage to sin or God.
I will happily add that the different perspectives on salvation were eventually reconciled in the Joint Declaration On The Doctrine of Justification, which heals a lot of this huge theological divide.