Doing a large amount of jumping jacks can get your muscles used to that type of movement and work out the muscles to make your movements faster. I would not recommend bulking up too much because this will increase your strength but slow you down, something you definitely do not want for a goalie.
Do a lot of squats, and high jumps. Make sure to stretch all of your extremeties and your core daily. You will need to activate the fast twitch muscle tissue and keep it strong. Do lots of shootout drills, and definitely learn how to roll when you hit the ground.
Getting your legs stronger (do leg press, squats, leg extensions, etc. ), and get your cardio up by jogging, stair master, and practice getting up and down as fast as you can.
