Having someone run his/her fingers through your hair is one of the most relaxing things you can feel, especially when you're stresed out. Most of the de-stressing qualities of scalp massage comes from stimulation of the scalp, which increases blood flow (and also makes your hair grow faster!).
If you're overwhelmed at work and don't have a massage buddy hanging around then opt for the next best thing: Giving yourself a massage. Check out this video to learn how.