I try to remove the source of the stress. If that doesn't work or can't be done, I've found physical exercise good, also just knowing that I'm working on a solution to what's caused it often helps me to feel better. Singing loudly is good too, and playing drums, if it can be done without annoying anybody. I can see how listening to music could work, after all, music is supposed to affect the emotions. I find the effect stronger when I play it rather than just listen to it. I guess any Aspie stimming method might be tried. Most of them seem to involve rhythmical movement.
Pets can help, but a dog can make it worse unless you've really got the time.
Being with somebody I feel safe with really helps.
I noticed that after a scary rollercoaster ride I felt as if all the anxiety had been squeezed out of me, and I was calmer than I'd been for ages, but the effect only lasted an hour or so.