Until the 15th of this month US Civil War records can be accessed free on Fold3.com, which archives military records. You just create an account (also free) and you can search and browse the collection. This is in celebration of Confederate History Month. (How often do you see companies promoting that these days?)
What's interesting about this collection is that it includes pensioner files (ie. dependents too). Thus, if you've hit a stumbling block with a certain branch in the tree, these pensioner files include the names of all children under 16 as they received benefits. They can map out an entire family for you and are invaluable, no matter on which side your ancestors fought.