I subscribe to Layers and Photoshop User (Photoshop User automatically as a member of NAPP). As was mentioned previously, Layers deals with all the Adobe products, while Photoshop User is, as the name says

, for the Photoshop user. Unless you have one of the other Adobe products like After Effects, Illustrator, GoLive, and such, Layers is probably not the magazine you are looking for since Photoshop coverage is pretty limited. Photoshop User, on the other hand, is an excellent resource if you only have Photoshop.
BTW, NAPP is well worth the money if you are serious about your Photoshop and the graphics profession.
HTH,