Most Americans have been brainwashed into thinking A. their wants are actually needs, and B. they are entitled to all of those supposed "needs". Time to let go of that and realize that living simply actually means "living happier and more awesome". As a bonus, using less disposable stuff not only saves you money, it is also more eco-friendly (funny how the two seem to collide so often.)
Here is an incomplete list of things you do not need to buy, ever:
I hate that people have been tricked into thinking that "trying to cover up the smell of the garbage you haven't taken out in 2 weeks with sickly, chemically flower scent" is the same thing as "cleaning". Just keep your hovel relatively clean, open a damn window, and never buy that shit again.
fancy toilet paper
Just buy the cheap, regular stuff. It still functions, and also is less likely to fill your bathroom with squeezably-soft fuzzy toilet paper lint.
Would you like some caviar with that?
Use toilet paper.
Use cloth. No, I'm serious. Cut up an old t-shirt, use to clean, mop, dry hands, etc, and have a bin (or pile) in your kitchen for the dirty ones. Wash them with the other dirty towels. Same goes for stuff like paper plates, etc.
any bathroom/kitchen cleanser that is not baking soda/vinegar
Not only clean, but deodorized and toxic chemical-free. I'll eventually devote an entire post to all the things you can do with these two common items, but for now, try this instead using of scrubbing cleansers and the like: Sprinkle baking soda, splash on a bit of vinegar, delight in the cool fizzy action, then scrub and rinse.
There are people who would be amazed if clean, drinkable water came out of a faucet in their house. Get a reusable bottle and learn to love your tap water.
Take all your mail and harvest the envelopes. Black out the old addresses and glue some new labels on top of them. Tape or glue the flaps. Or fold a sheet of recycled paper in thirds and tape the ends. Use grocery bag paper, wrapping paper, etc. You get the idea. There are also plenty of online tutorials for making your own fancy, "real" envelopes. Get creative. Save all bubble envelopes and packing you get in the mail, too.
If you're in college or work in an office, you probably have a lot of handouts and memos printed on only one side. Take all your old ones, flip to the clean side, staple or sew together. If you're crafty, you can even bind them into real books.
plastic storage containers
Use shoe boxes, shipping boxes, or hell, even garbage bags to organize your closets. A Sharpie works wonders for labeling.
Know of any more things that can be deleted from your life? Comment! Let me know if I have permission to post them later (with credit to you, of course!)