If you're going with saluting indoors from "Children of the Gods", I believe that was actually incorrect. Ditto Hammond wearing his lid in the very first scene. ("Children of the Gods" got a lot of military stuff incorrect.) I suppose if they're doing a ceremony like promotion (Sam from Capt to Major) and Daniel's funeral, you can have saluting (I have no idea, but I assume you can) but if you remember "Avalon", Cam doesn't salute Landry in his office. And he's not wearing his lid, because you don't wear headgear indoors.

ETA: See my comment below. Maybe "Children of the Gods" wasn't wrong after all! Since Jack and Sam were reporting in (the briefing, Sam's first scene) then it was appropriate they saluted. And Cam should have saluted, because he was reporting in in "Avalon". Huh.

My last ETA, I *swear*! ETA2: Though I can easily believe that the SGC is one of those "no hat, no salute" areas since we never see them salute after the first couple of years.