Graphologists, those who make a scientific study of handwriting, have differing opinions about whether examining a sample of handwriting can reveal the sex of the author. Graphologists tend to focus on a person's personality traits, and claim that a person with feminine traits may have feminine handwriting whether the author is biologically female or not.
Males and females do tend to have identifiably different handwriting. The general public is able to identify the sex of the author of a sample of handwriting approximately two-thirds of the time. Graphologists argue that the influence of personality overrides the influence of gender and the gender of the writer cannot be identified with precision.
Transsexual Road Map's website describes the handwriting of English-speaking males as "hurried, uneven, messy, spiking, sloping and bold." These characteristics are sometimes seen in those who speak other languages as well, but the commonalities are believed to be more cultural than inherent.
Transsexual Road Map's website suggests that English-speaking female handwriting is often "neat, even, round, small, ornate and symmetrical." The commonalities are, again, likely cultural.
Another element of graphology is word choice. Men and women, broadly speaking, use language slightly differently. Women tend to speak more about people and relationships, using words like "I, you, their, myself" while men tend to talk more about things and quantities, using words like "that, one, more, a."
handwriting image by Christopher Dodge from Fotolia.com