Music - when you're stressing listening to music can actually lower your blood pressure, relax your body, and calm your mind
Take a walk - any form of exercise increases the blood flow to the brain which in turn increases your thinking skills. Also exercise releases endorphins that will lift your spirits and your mood.
Laugh - Laughter releases endorphins and reduces the level of stress hormones; it offers a distraction from negative emotions; use laughter to connect with others
Breath - Just breath! Take a couple of strong, deep breaths - inhale through your nose, hold for 6 seconds, then exhale through your mouth. While you are doing this, concentrate on your breath and breathing patterns.
Play Games - Even just a simple game of online tetris can help you to reduce stress while giving you a break from your studies. Its fun and free online games are easy to find. A site I like to use for games and funny flash videos is Albino Black Sheep.
I just thought I'd share these becasue they all have been helping me through these last few weeks! If you'd like to read up on stress relief for yourself, this is where I found some great ideas!