For fans of the Iron Man comic books, it was somewhat surprising to hear that the villain in the first movie was going to be The Iron Monger, as opposed to Tony Stark’s longtime adversary, The Mandarin. But that doesn’t mean that the villain’s presence isn’t felt throughout the course of the story. During Iron Man’s origin sequence in the cave, it's revealed that the terrorist organization holding him hostage is known as The Ten Rings. There's even a Ten Rings banner hanging up in the cave.
This is obviously a reference to The Mandarin, who's powered by ten alien rings that each harnesses a different power. This could have been a harmless wink at the audience, or a hint at bigger things to come in the sequels. We certainly wouldn't mind The Ten Rings stepping out of the shadows and becoming a major threat in Iron Man 3.