Since there's only about a month of summer vacation left and I like to get started on room setup at the very beginning of August (saves stress later), I just finished ordering some basic room materials for the year.
I don't know any teacher at a high-needs school who doesn't buy his or her own bulletin board trimmers, name tags, charts, stickers, heavy-duty folders and other general supplies. Some of these we order because we have specific desires. For instance, I order my own folders because I would prefer to buy a couple sets of heavy-duty, extra-large folders annually rather than a couple hundred cheaper ones (which my school doesn't supply anyway). I also bought a mess of these, which came highly recommended by teacher and trainer alike at the Institute I attended. (I could just get pencils from the supply closet.)
But a lot of these things just aren't provided. If I don't buy incentive charts, I can make my own (time-consuming). If I don't buy bulletin board trimmer, then the boards won't be trimmed (ugly; also, it requires being far neater in cutting the paper since trim hides rough edges). If I don't buy stickers, I won't have any. And again: this is something that many - most - teachers have to do every year. This is not a job requirement for other professions - CPAs do not need to buy their own green visors and calculators; doctors do not purchase their own surgical tools, etc. This is yet another de facto paycut for teachers, especially since when school budgets are cut, supply budgets are cut - but children still need the same things. (This is also why big line items for supplies in central office budgets are really irritating.)
As it happens, this means I've already spent my federal tax deduction ($250) for school supplies before the year has started.