Air flow is the key. The point of sweating is to remove heat, I believe. It can't be removed if it goes into the c/a, which seems to act like a huge heat reservoir. To fight the heat in summer, I usually do the following:
Wear UnderArmour heat gear: The stuff is skin-tight. It does wick the sweat off of you well enough.
No socks/pants/etc.: I wear running shorts. More sweat than wanted gets in the crease, but a towel takes care of that. I was amazed at the difference wearing shorts made.
Take my gloves off once in a while: I don't know about you, but I usually follow my extremities. If my hands are warm, so am I. If they're cold, I'm cold. Letting some heat come off helps.
Skate around and lift up my jersey and c/a: I'll often, during breaks, do this. It lets a lot of airflow come in and pull some heat out of the c/a. We can't pour water down our backs, so it's the closest we can get.
Remove the helmet as much as possible: This is the most simple, but most effective tool for me.
Dry off as much as possible: I like to consistently wipe away the sweat in my hair and on my skin so new sweat can come out with more of that stupid heat
I don't think there's any one cure-all. I used to play 2-hour pickups during the summer, and I swear it was like 110º to 120ºF in my equipment. Of course, stay hydrated all day up till you go on the rink. These little things really helped make it more bearable.