I have a SweatVac skullcap from Wickie Wear that seems to work great in keeping my helmet from taking all the sweat. Keeps the sweat out of my eyes, too.

http://www.wickiewear.com/

There are other companies that make similar products. I know lots of people like buffs, but I can't see having something bulky on in the summer time. I am considering one for winter, though.

Karen