Sonax Full Effect Wheel Cleaner, Griots Heavy Duty Wheel Cleaner, 1z Colortec Wheel Cleaner, CarPro Iron X ect. Essentially any good wheel cleaner you can buy at a dedicated automotive detailing store(Carzilla for the Calgary folk) will do the trick.
Half the battle is making sure you have the right brushes to remove the grime as the product needs to be agitated. Also if your wheels are really caked you may need to clean them a few times.
Once you have the wheels spotless it doesn't hurt to apply some sort of protection to repel contaminants and make them easier to clean in the future.