J.H.
This is a company we are considering using for our fundraiser t-shirts next year - http://www.urnameonit.com/
I have also used http://www.ideasnmotion.com/ before and was always really happy with their quality and customer service.
They actually do the printing on shirts ... not sure if you meant you wanted just plain shirts ... if so, I'm not sure if they can help but maybe they can point you in the right direction!
Good luck!