No sex. Technically no music, either, but people tend to ignore that and I've just mostly listened to Sufi songs.
We're not having sex here, anyway. Surprising, right?
One of the things I like about Ramadan is that it's a fairly secular thing. Or at least enough of it is that I know a number of non-Muslims who only observe it for these aspects.
It's the main reason for me, too. Setting aside some time to learn about Islam is the other (which is a religious reason to do it for Muslims, too, and it's still not really about pleasing any deities).