Preaching courses are absolute essential courses in seminary but seem to be given lower priority today in place of leadership. Here are a few of my favorite books on practical ministry that I think are absolutely excellent.

On preaching:

Haddon Robinson, Biblical Preaching, 2nd ed. (Grand Rapids: Baker, 2001).

Donald R. Sunukjian, Invitation to Biblical Preaching: Proclaiming Truth with Clarity and Relevance (Grand Rapids: Kregel, 2007).

Bryan Chapell, Christ-Centered Preaching: Redeeming the Expository Sermon.  Grand Rapids: Baker, 1994, 2005.

On Christian leadership:

George Barna, A Fish Out of Water: 9 Strategies to Maximize your God-given Leadership Potential (Integrity Publishers, 2002).

• this last one might not be used much in seminary but I think is chocked-full of valuable information to know.