I grew up with the knowledge that I was Jewish, a fondness of Israeli dances, and a small vocabulary of Yiddish exclamations and curses. That was pretty much it. Although I've tried at various times to add more Judaism into my life, it never really took. My husband took "how to Jew" classes with me when we were newly married, and he's the one who remembers stuff, so he's the one who cooks the latkes and explained the concept of Tzedakah to our son this year.
When our son was in a Jewish preschool, it was much easier to remember and celebrate the holidays. But he's in high school now and we've gotten pretty lax.
The one thing we always do is the very minor holiday Hanukkah, and it's not to compete with Christmas, which my husband utterly adores. I think it's partially because it's easy, and partially because it's pretty -- lighting candles and singing blessings, what could be nicer? -- but also because as I get older, Christmastime is the time of year when, paradoxically, I feel the most Jewish. I'm always grateful when they fall sufficiently far enough away from each other that the Menorah lights aren't overshadowed by Christmas tree lights.