For a very good general essay on abortion, this piece by Probe Ministries' Sue Bohlin is one of the best around. Just click the title of this post to go right there.
The article is posted at the site of Leadership University (a valuable source for common sense on several issues) and their Medicine/Bioethics section has some terrific pro-life material gathered from around the net.
Sue also has several essays over at the Probe Ministries site you'd do well to check out too.