Most of my pet peeves about laundry can be summed up in a few words: get your laundry out when it's done. Seriously. But since that doesn't make a post and since I do have more pet peeves than that, let's get started.
How people do their laundry is their business. If they want to mix everything up and turn their white undies pink, that's their business unless they're throwing my laundry in with it. However, using the whole washer to wash or dry two small things is not okay. I know it's not as easy to wash an article of clothing by hand as it is to wash a dish by hand, but trust me, it can be done.
Seeing the dryer used for one item is equally annoying, but I can understand if you're in a rush. If you're not in a rush, just hang the thing to dry. It'll dry eventually. Really. If it wrinkles, you can iron it or hang it up in the bathroom while you take a shower. The really annoying part is watching people grab everything from the dryer except two things because everything else is dry, then start the dryer up again for the full cycle. Why do you do this? The clothes weren't designed to withstand such things, and all that heat could do them harm. Shrunken shirts, anyone?
Then there are the people who don't clean up after themselves. Most laundry areas don't lend themselves to a space for a trash can, but surely there's a space for one nearby, even if it's in the next room. Pick up your messes of fabric sheets and lint and put them in the trash can, not on top of the washer and dryer. That saves them from getting all over your clean clothes when the clothes leave the dryer.
Don't forget that your clothes are in the washer or dryer in the first place. It's one thing to have something come up while you were doing laundry, but leaving them there all day when you know other people are going to do laundry isn't cool. This one comes from four years of college and sharing washers and dryers with a dorm full of students. People would start a load of laundry and forget about it, leaving the next person who came along to toss the load in the dryer or on the table because the owner of the clothes couldn't be reached. Look, no one wants to touch your undies unless they're sleeping with you, helped create you, or have an underwear fetish. Do the world a favor and get your laundry out on time.
And if you ever find yourself doing my laundry, never put my favorite gray sweater in the dryer. Washer, yes. Dryer, no.