I wear wool t-shirts. Granted, it doesn't get all that hot here in Seattle, but it feels hot to me...

No stink, no cling, no moisture held captive against my dainty skin.

I have wool stuff from Duofold, Icebreaker, and Ibex. I much prefer Ibex. www.ibexwear.com Their stuff ain't cheap, but it is fabulous and replaces 3 or 4 regular shirts. Be sure to check out there outlet/sale section. Sometimes you can find theirs at Sierra Trading Post for pretty good prices. www.sierratradingpost.com

Otherwise, I second the suggestion to check out Target for wicking loose comfy t-shirts. Target is one of my favorite places because they have such decent stuff for such decent prices. (and they give good wages and benefits to their employees)