It depends on the situation.
We'll be going to my husband's company Christmas party this week. I will probably shake hands with each new person I meet.
Last night we were at our son's holiday concert. I hugged the women I know well and I shook hands with their husbands, many of whom I'd not previously met.
If I were at a casual gathering in someone's home and the guests were primarily women, I would probably not extend my hand. I often get the feeling that women don't care to shake hands.
A casual gathering at my Dad's house, though, when I'm meeting his male friends for the first time? I shake hands.