I wouldn't be surprised if many people are already doing this, but ride your bike whenever you can and leave your car parked.
Think about where you need to go during the week and see if you can use your bike for any of the errands.
Also, if you happen to be lucky enough to not work far from home, ride your bike to work. Maybe not everyday, but what about once or twice a week? Even that will help you save money.
Don't forget your helmet!