I feel certain that at some point we are all going to be living in great floating space cities, dodging cylons and repairing dilithium crystals. It just has to be true. So even though NASA has stopped flying manned missions, there are lots of people thinking about the practicalities of long-term space travel: pooping, peeing, and, of course, sex. Anyone with even the slightest interest in space travel should have read Mary Roach's Packing for Mars already. She gets into all the meaty bits about elimination and copulation, including whether or not humans have done it in space (probably not, but if they have nobody's talking.)
Sex in zero gravity ain't simple. Grabbing onto a person without going flying seems challenging, if not impossible—every action has an opposite reaction. Which is why I think this 2suit is so cool. Invented by Vanna Bonta, who happens to be married to one of the SpaceShipOne avionics engineers, the 2suit is designed to stabilize humans in zero g so they can snuggle, hug, or have sex. It's got a harness that can stick to a wall, and zippers and velcro to undo the whole thing (and be nude) or hook two suits together to make a little sex bag to hang out in.
Obviously our giant flying biodomes will have some kind of gravity engine holding us to the ground, but in the meantime, this doesn't seem like such a bad option.