The hair apparent
Is bawdiness the new feminism, as Slate's Girls Gone Wild piece contends? This article reminded me of an AP style rule that may be rising in utility.
Use blond for the adjective, whether you're talking about men or women or both. He had cropped blond hair and boyish good looks -- and a glamorous blond fiancee.
Use blond as a noun referring to men, and blonde as the noun referring to women. She always had preferred blonds. She wished the other blondes weren't such competition.
Apply the same rules to brunet and brunette (although you seldom see brunet used as an adjective).
You are, however, likely to see blonde and blond used wrong quite a bit.