IMDB to the rescue. I thought maybe they just had the same composer (since everything Danny Elfman does sounds the same, and most Michael Bay flicks have similar scores) but Transformers original music was done by Steve Jablonsky. When I think of the music in it, I think of the vague hints of techno at the end credits, punctuating Optimus' monologue and Starscream's escape.
National Treasure was directed by Jon Turtletaub, and scored by Trevor Rabin. And Doc, as a minor movie geek, I was thrilled when you revealed the source of the music and I was right in my guess!