David Sills is a professor at Southern Seminary and recently spoke at the Desiring God National Conference. His books, The Missionary Call and Reaching and Teaching are excellent!
You may not know however that he has started a ministry called Reaching and Teaching. Check out the resource page for excellent articles and powerpoint presentations related to missions. You will be greatly helped!
One of David's emphasis is on reaching illiterate people groups (most unreached groups are illiterate). Considering that most people who go to the mission field have studied at a master's level, it is worth our time to think about how to teach those whose education is so much different from ours.
Darren Carlson is the Founder and President of Training Leaders International. As President, Darren oversees the general direction of the ministry and serves as an advocate for pastors with little access to formal training and thoughtful cross-cultural theological engagement. You can connect with him on Facebook and Twitter.