I found this neat site that lets you choose from a bunch of different major U.S. cities and then set off a fireworks display using the Shockwave Flash player. Wouldn't you know it? Detroit was one of the options :)! It is a fun little waste of time. You just click the buttons under the city display and shoot off different types of fireworks. There is even a grand finale button you can hit for a real whiz-bang finish.
Go there now, and waste some time!