I was doing some research because, living in Toronto, I figured there would be alot of options - the stains in your clothes are actually caused by the aluminum in the antiperspirant (if you use those) and it gets baked in due to a chemical process.. to take it out, make a paste of baking soda and a bit of water and scrub it in with an old toothbrush. let it sit in the sun a few hours then activate the baking soda by scrubbing with a vinegar-dipped toothbrush. then handwash or chuck in the machine. If that doesnt work, next squeeze out some lemon juice (From a REAL lemon - juice in the bottle has dye!) and let it sit in the sun til it dries. the lemon is a bleaching agent and when you wash your shirt again the stains should be pretty much completely removed.
Also, Uncle Tom's makes a nice smelling antiperspirant with honeysuckle which can be bought at health stores, but it doesnt last very long and I find i have to reapply it every hour or two.