"One of the most beautiful sights is a urine dump at sunset, because as the stuff comes out [in space] and as it hits the exit nozzle, it instantly flashes into 10 million little ice crystals, which go out almost in a hemisphere, because, you know, you're exiting into essentially a perfect vacuum, and so the stuff goes in every direction, and radially out from the spacecraft at relatively high velocity. It's surprising, and it's an incredible stream - a spray of sparkles almost. It's really a spectacular sight." -Russell Schweickart, Apollo astronaut.

During rocket take-off (and landing, I think), astronauts wear diapers. During flight, they use texas catheters, IIRC.