I swear by Ex Officio long-sleeved shirts. Feel like cotton but quicker-drying and lighter. Finding ones with good-sized pockets has gotten tougher -- the women's ones used to have the same pockets as the mens, which they seem to have gotten rid of in pursuit of style, boo. The men's ones are comfy, too -- they're really not strongly shaped garments, so as long as the sleeves aren't comically/uncomfortably long, the men's ones should work too.