Sure , there are many alternatives, but none as good as dynomat. That stuff does more than stopage of rattles, it actually improves sound. It is a very dense material, and it dampens the sound eviornment. It will quiet your ride, and allow more sound from your audio system to remain in the vehicle as opposed to disapating outside the car.
Alternatives:
Socks
Old T-shirt
Rag
Roadkill