As Islam grows–more by birth rate than adult conversion–there are new realities that we must be aware of as Christians (Muslims are 1/5 of the worlds total population – Christians are 1/3). Understanding is the first step. Engagement only follows after we understand. I came across this video from the wall street journal which highlights some interesting observations about Europe and America.
What do Muslims believe? A great place to start is The Baker Pocket Guide to World Religions: What Every Christian Needs to Know by Gerald McDermott.
Also, an excellent mp3 overview you can download is Decoding Islam: Understanding the Middle East Conflict in a Whole New Light– Alan Shlemon (Stand to Reason)