First guess sounds like a B-2. Second guess is that you misjudged the size and it was an F-117. Those do have two vert tails, although they're angled.
And Chairboy, you're right, most of the time the B-2 makes as much noise as anything else, but they can make the engines very very quiet when they want to. Saw one do a flyby at a football game one time, sounded like a slight wind was blowing, nothing else. Really freakin' weird.