Judging by some of the responses (or, rather, respondents) so far, I’m starting to wonder if breaking down the results by gender is less interesting than breaking them down by political orientation.
Quick, someone go to freerepublic and post the question there.
29, female, shower-pisser here. In fact, if my husband and I are taking a shower together, we’ll still pee in there … I crouch over the drain when I gotta go, and he aims for it when it’s his turn.
I have no google-fu, but if my memory serves, your kitchen sink is the Dirtiest place in the house, followed by the bathroom sink, the bathtub (shower or no), the cleanest being your toilet. This is all considering regular cleaning. During a major pile-up in the only bathroom in my house, I will piss in the bathtub and rinse it down.
Pee in the shower while showering- Daily, or close to it.
Pee in the shower from outside- Did it once that I can remember, while repairing the toilet.
Pee in kitchen or bathroom sink- Would not. No way.
Pee in utility sink in basement- Never have but might.
Pee in the plastic tub where the washer drains- Do it often. Have a hose handy to “flush”. The tub drains to floor drain. My only toilet is two floors up.
Pee in my yard- Yes, sometimes in a secluded spot. Sometimes when I’m mowing or working in the yard I get mud or dog poop on my shoes and don’t want to track it inside.
I’m glad it works for you, but I’d have to go with my friend Seinfeld’s advice: “But the thing you don’t realize is that there’s good naked and bad naked. Naked hair brushing, good; naked crouching, bad.” 
I was very surprised to hear from a male friend that guys don’t jack off every time they shower. I mean, you’re soaping up your penis and presumably rubbing it somehow to clean it, right? You’re right there, how do you not jack off??
I think every guy does it at least once in their teens.
Once. 
Female, I pee in the shower.
I don’t regularly but if I have to piss whilst showering I’m not going to hop out or hold it, I just practice my aim like Maiira. Same plumbing kids, let’s not be silly here.
I was hunting from my new tree stand this year when I realized that as plush and nice as I had built my hunting shack, I had neglected to put in a bathroom, CURSES!
Most stand hunters pee in a bottle with an O-ring to stop the scent from escaping. Do you know how hard it is for a girl to pee in a bottle!? I ended up getting a Lady J, a ridiculous apparatus that while embarrassing, is extremely effective.
I think Freudian Slit makes a good point about non-standard peeing. Using that adapter I can pee standing up but it takes for ever to get started. Girls don’t pee standing up,* it’s weird, it’s not the way.*
Compared to the slimy gunk that normally gets scrubbed off your skin, sterile urine that is quickly diluted to lower-than-homeopathic levels is no big thing. Add to that it’s usually done within 15 seconds of stepping into the shower, there’s another 5-10 minute hot water rinse of the tub immediately following. Now if you’re one of the sickos who POOs in the shower and then smooshes it down the drain with your toes…
Madonna sez it helps cure athlete’s foot. Cecil begs to differ, however.
In the morning I get up, start the water for the shower, and during the 2-3 minutes it takes for it to warm up, I pee in the toilet. If, as to gigi’s point, Mr. Happy comes knockin’ midst-shower, I’ll whack off (assuming the wife hasn’t taken care of it already) and then I’ll pee to help rinse the cum down the drain. But if I haven’t cum in there, I don’t pee in there.
After I pee in the shower, I squirt a little shampoo onto the tub floor and lather it up with my foot while the water washes it down the drain. Since my wife generally cleans the tub, I think it’s the least I can do for her.