I've been wanting to try this for ages, but it wasn't until today, when the stores were full of so much pretty white clothing, that I got up the energy. It was really H&M's spring collection, most of which is made of white, recycled cotton and is seriously pretty, that got me to do it. That, and the Jim Jarmusch t-shirts at Uniqlo.
So... tea dyeing. I looked up about a thousand tutorials, but most of them were contradictory or not very specific so I got fed up and just sort of did what I thought would work. I was a little worried because several sites mentioned that the tannic acids in tea break down cloth, but eventually realized they mean that happens over about fifty years, which is important if you're making heirloom quilts but not if you just want a pretty dress to wear for the next few summers. Tea makes fabric look nice and antique, and it's a good dye because tea stains everything. Even tea cups. But if you drink wine out of them the stains will break up.
Anyway, here's what you do:
Buy a really pretty white dress even though you look awful in white. It has to be cotton or another natural fiber, or this won't work.
Buy a big cheap stock pot. Or use your normal one, since nothing you couldn't consume anyway is going into this dye. Pour in about two gallons of water and boil it. Meanwhile, unwrap and tie together twenty Lipton tea bags. Boil those for a couple minutes or until the water turns... well, into tea. Pretty dark tea. Turn off the heat.
Soak the piece of clothing very thoroughly in warm water. This is important (or it has been every other time I've dyed anything). Stick it into the pot of tea, and use a wooden spoon to stir it around for a while so that it dyes evenly. Pretend you're in the laundry dungeon of a medieval castle. They show those in movies weirdly often. Didn't some people fall into vats of purple dye in one once? Use the spoon to pull out an edge every minute or so to see how dark it's getting.
When the cloth is a little bit darker than you ultimately want it to be, take the stock pot into the bathroom, put it in the tub, and carefully use the spoon to lift the dress out. It's going to be hot, so be careful. If you're lucky it'll have those little ribbons meant to keep it on the hanger, and you can grab those. Turn on the shower (try to move the pot of tea so it doesn't get more water in it) and rinse the dress with cold water, wringing it until the water coming out of it is clear. Your bathtub will look like someone with liver failure peed in it, but don't worry about that.
Wring out the dress and hang it up to dry. If it's too light, put it back in the pot for a few more minutes. Then start randomly chucking all the white things you own into the pot because you hate white/wish that cute nightshirt with the owl didn't have sweat stains on it (note: they are still visible, but now the shirt is prettier). Try putting a non-natural fiber dress in, just to see what happens. It can't hurt (but it won't do anything besides make the dress smell like tea). Don't forget to stir and check the clothes often. I left my dress in for about seven minutes and it got pretty brown. One of the shirts I dyed turned just as brown in about two minutes.
At some point you should do something to fix the color in the cloth. I'm told that white vinegar and alum can both do this. Several sites said to let the dress air dry and then use a hot iron to fix the color. I don't have an iron but I probably should, and I don't really want my dress to smell like vinegar, so I'll probably go get one tomorrow. And then I'll be careful when I put these things in the laundry, although if all the color washes out I can just dye them again.
I might wear the dress without using a fixative first, just to see how I feel about it. Right now it is soaking in a pot of that bright red Passion tea they have at Starbucks, because I'm trying to make it look like antique rose instead of just antique. I'm not that hopeful, though... the nice brownish color seems to be all gone and it's a pretty-but-not-me shade of blush. Might have to do a second Lipton bath. I kind of like the idea of just soaking it in various things until it suddenly turns exactly the color I want. I'll let you know how that goes.