Some useful links to learn more about the Civil War:
American Battlefield Trust
Battleground preservation with overview of battles and statistics
CivilWarTalk
Online community of Historians, Skirmishers, Re-enactors and Enthusiasts
Blue And Gray Education Society
Premier organization for field studies and tours of battlefields and historic sites
Index - War of the Rebellion: Official Records of the Union and Confederate Armies
Cornell index- linked to actual documents in Hathitrust
Library of Congress Civil War Maps
High resolution, downloadable maps of the Civil War
Battles of the American Civil War
A chronological tour and interactive map of decisive Civil War battles
Civil War Photo Collection
Library of Congress photography and drawing collection related to the Civil War
History.net Civil War
On-line magazine of topics regarding the Civil War
Harper's Weekly
Digitized Harper's Weekly along with other great resources on this site
CWRT Congress
Information on all other Civil War Round Table activities worldwide
Inland Empire Civil War Round Table
An active Civil War Round Table in Southern California
Soldiers and Sailor's Database
National Park Service Civil War database covering many topics