You know where Gandalf is talking to Aragorn and says "There's a veiling shadow that glowers in the East..." Well, that is refered to by Legolas as they are riding toward Helm's Deep. Gandalf has asked him what he sees in the distance. Legolas sees "a veiling shadow that some power lays upon the land".
Also, there is a scene in the preview where Eomer is riding along through some trees. I though at first this was when he was about to stumble upon the two young hobbits, but I believe this is after the battle of Helm's Deep and he is riding toward Isengard, when they are passing through the trees.
-Kevin