Hmmm, some people like to smoke weed, and I'm sure if you could get your hands on some low level opiates, those would help too.
How are you administering the meth? Different forms of administration have different comedowns. Smoking is supposedly the worst comedown (though I personally wouldn't know), snorting is bad but better than smoking, IVing I would personally place as the next best comedown, though I'm sure many would disagree. Orally, the comedown ain't that bad at all. Perhaps you should experiment with doing drugs different ways and see how that changes the comedown for you.
Other things that help the comedown:
-drinking lots of water, during and after your tweaking session (this is really important, you'd be amazed by how much it helps)
-vitamins, and some sort of food/soda to boost your blood sugar
-intense exercise; it will tire you out and help flush toxins out of your body....it's also fun to workout when you are no longer really tweaking but still feeling a little wired (don't exercise when you are actually rushing as you could injure your heart)