Some excellent books have been published that deal with direct Union efforts against the Charleston defenses. Two of the best are Patrick Brennan's Secessionville: Assault on Charleston and Stephen Wise's phenomenal study, Gate of Hell: Campaign for Charleston Harbor, 1863.
However, the coastal region between Charleston and Savannah was an active front throughout the war. An important aspect of these coastal operations were the repeated U.S. attempts to cut the vital Charleston and Savannah Railroad, perhaps most notably during the October 1862 Pocotaligo Expedition and again with two attempts in late 1864, the November 30 Battle of Honey Hill and the fight a week later at Tulifiny Crossroads.
This brings me to the reason for this post. The release date is still way off in the future (February 2008), but University of South Carolina Press will be publishing Vital Rails: The Civil War History of the Charleston & Savannah Railroad. I haven't been able to obtain a description of this book, but it sounds interesting and makes me wonder what its focus is on beyond the obvious.
[addendum: 6/7/07 - USC Press sent me a copy of the book description that will appear in the next catalog. It will indeed be a full economic, military, and logistical study of the railroad. I am very interested in its discussion of the coastline's mobile defense system (of which this railroad was critical) devised by Robert E. Lee during his stint as Dept. commander.]