Being from humid NC, I swear by Halo headbands. They really do a good job at sopping up the sweat and keeping it from dripping all over your face. I am a head/face sweater, so I have to wear these on rides in humid weather, or even hot and dry weather like we've been having here in eastern WA.
They really last a long time, too. I bought mine years ago, and they are still going strong. Did not find them here on TE, but they sell them at REI and many places online, like Amazon:
http://www.amazon.com/Halo-Headbands.../dp/B0085QI8VO
Hope this helps!