I saw some things about Stack Exchange wikis, and it seems like linking to common papers, wikipedia articles, helpful resources might be something helpful to users.
I've already seen two people (one of whom was me) link to Lockhart's Lament in several different threads. This makes sense, because the "beauty of mathematics" argument is going to come up in Q/A about teaching math.
If there's not some sort of wiki we could put this on, how should we deal with this issue?
I would not know of any "wiki" internal to the SE system that could be used to this end. There exist so-called "tag wikis" where descriptions of the subject of the tags can be included.
Some sites have very elaborate one for some tags see https://stackoverflow.com/tags/php/info for an example. Yet, this seems somewhat orthogonal to the issue at hand.
Generally speaking, an answer on an SE site should be as self-contained as possible. It should make sense independently of external resources. Of course it can be inevitable to link to external resources, but as a general rule try to include the most pertinent part of the thing you quote in the answer.
On some sites where very simlar questions came up over and over again they decided to create "general versions" of common questions with elaborate abswers and then close new questions as duplicates of these questions. Such questions (and their answers) can be put into "community wiki" mode (perhaps it is this you mean), which makes them easier to edit (lower point limit for editing) and slightly detaches them from the account of the original poster in that they do not get points anymore for it.
