Fold3, a paid subscription site that specializes in military records, is providing free access to their U.S. Civil War records from April 1-15.
On the registration page, to the far right, is a free registration option with no credit card required. It does work and you can view the images.
I was able to find, view, and download my 2xgreat-grandfather's compiled service record. It included a receipt with his signature that was not included in the packet received from NARA by a cousin.