I found this site when I first began my research on the Regular cavalry, and have found it to be a treasure trove of information. The researcher, Edward Czarnecki, has created a wonderful site that is in my opinion the single most comprehensive site on the Regulars in the Civil War on the internet.
Mr. Czarnecki has regimental histories for most of the Regular regiments of all three arms from two different sources. The first is Frederick H. Dyer’s A Compendium of the War of the Rebellion, and the second is T.F. Rodenbough’s 1896 The Army of the United States. Czarnecki has excerpted unit histories from both of these works, arranged in numerical order by arm. For the infantry regiments, he even has unit rosters.
This site also contains excellent references for tactics of the period. There are locations for contemporary infantry, cavalry and artillery tactics manuals, including Philip St. George Cooke’s 1862 Cavalry Tactics. Additionally, there are references for West Point curriculum for each year of the war, and the officers who served as faculty. Even military administration is addressed, with copies of the 1861 version of US Army Regulations and customs of the service for officers, noncommissioned officers and soldiers. Several manuals for volunteer units are also available on the site.
Overall, Edward Czarnecki has created an easily navigable site full of valuable information to the Civil War researcher, whether researching Regular or volunteer units and tactics.