• "Key Resources" are now called Relevant Websites.
• "Key Concepts" are now at the very top.
• I added "Note: Don't be intimidated by the length of this list. Most of these references aren't prerequisite. Only a small fraction is necessary to follow most of the posts and discussions on LessWrong. Before giving up rather just go ahead and read the Sequences, you'll see it's much easier to understand than this list makes it look like. And if you've trouble understanding some concept, just ask in the comments or come back and see if you can find some explanation via this companion."

I know that some entries are only tangentially related to LW, but I wanted to compile a list that gives you as much as possible background knowledge to understand and participate on LW and integrate into the community. I believe that programming is a essential field of knowledge and that Go is not just very popular with people interested in LW related content but also one of the first hard AI problems people can learn about by simply playing a game.

About ordering it from easiest to most challenging. Well, I can't do that. First of all it would likely mess up the categories and it is not clear to me what is easy and what not. This list is the culmination of feedback I received from asking, "What should I learn?" That is, although I'm reasonable sure that all of the items are of high quality as they were recommended by highly educated people who have read them, I haven't actually read most of it myself yet.