I shower at night. It means if one of my housemates beats me to it there’s no problem, as I’ve no where to be. I’d hate to have to spend the morning rushing to dry my hair because my housemate spent an hour in the bathroom and now I’m late for a lecture.
The thought of getting into bed without showering grosses me out. If I didn’t take a shower at night I would probably change my sheets every day. Besides , I have to get my makeup off and wash the …um… sweaty bits anyway, so I may as well shower. Sometimes I take one in the morning as well, if I need a little help waking up.
I shower at night - like the others I can’t stand going to bed dirty. I also don’t sweat much at night (especially in the winter) so I feel clean in the morning. My hair is so short these days that it’s no problem.
I always wash my hair at night because it’s long (just about getting to my backside now) and dries naturally, which takes about two hours. It gets turban-towelled up until it won’t soak through what I’m wearing, and then I just let it fall until it’s dry and brushable. Night showers are by far the most comfortable because you don’t have to get up out of a warm bed and then take off all your clothes, but I prefer to feel completely clean before going out to work. I know your body doesn’t sweat much while you’re asleep, but starting a new day after eleven hours of being unwashed doesn’t seem quite right to me…
Lucky you! If I leave my hair for four or five days I look as though I’ve been caught in the rain. 
I don’t go to bed until my hair’s brushed, so no bed-head problems there.
I shower at night probably about 50% of the time. I would never go to bed after a day where I got dirty/sweaty without a shower, but having an office job means there are plenty of days where that’s not an issue and I just hit the sack.
I do shower every morning with very few exceptions, so I guess half the time I’m showering twice a day. Never really thought about it that way. I guess I’m a sucker for hot water blasting all over.
Man, now I want to go home and take a shower. 
Jammer
Nighty-time female showerer here. I associate showering/bathing with going to bed and relaxation. I have short but thick hair. I do the shower cap thing at night, then wash my hair in the kitchen sink in the a.m. (and I use a hair-catcher so my sink doesn’t get all stopped up). I go to the barn and see my pony (and usually ride him) after work and cannot imagine going to bed smelling like a barn, especially in the hot and humid summer when that smell oozes out of my pores.
Well I guess if you wake up all sweaty and nasty you need a shower. I am not a sweaty person… I rarely sweat at all and actually only take a bath every 3 days or so unless I’ve done something to get grungy (or am having sex).
Somehow bedhead is never a problem. On the rare occasions when my hair looks funny in the morning, I just wet my brush and that takes care of it.