Some of the best info I have found on dispensationalism has come from articles on the net (folks like Timothy Morton). Here's a site for a church in Florida that has some pretty good sermons you can listen to (go to sermons and topics):
http://www.daytonabeachbaptist.com/index.cfm
Now this guy teaches that baptism for the Christian is a matter of liberty so some would say he leans toward hyper-dispensationalism, but I think I have a pretty good handle on sound doctrine and his sermons present some good instruction.
I didn't mean to imply anything negative about David Walker being a graduate of Ruckman's school. I have many of Ruckman's commentaries and books and have benfited from them although Ruckman isn't the greatest writer so maybe Walker presented the topic in a more clearer manner.