I actually asked for advice for self-control when feeling angry on formspring.me/AdviceAndHelp
Here's the response, which I felt was pretty good advice:

If you have been feeling stressed that could be why [you feel angry]. I suggest you:

- Take deep breaths.
- Try figuring out why you're so angry.
- If you feel like hitting something hit a pillow or something that you won't hurt or something that won't hurt you.
- Spend time alone for awhile.
- Express yourself; write in a notebook about what makes you mad or what person makes you mad & why.
- Let it leave your mind.
- Relax, breathe in & out.

& think of happier thoughts.

A quote that goes along:
"we can not control what happens to us, but you can control your attitude towards what happens to you, In that you will be mastering change without it mastering you."