I've actually been wearing a coolmax liner type thing (like a coolmax super thin skull cap, basically) and I notice my temperature seems a lot more regulated. If it's cold, my sweat doesn't freeze me, and if it's warm, the sweat goes away. I didn't think I'd like it as much as I do, but I wear it every time I ride now.

It wouldn't be enough in the winter, and we'll see in the heat of summer, but so far so good. I bought it on the cheap at REI, so it's got great "Live 2 Ride" "Ride 2 Live" motorcycle style graphics on it. My husband makes fun of me.