I've wanted to play around with some similar ideas for a while too, actually. I have a few loose high-level ideas - I know I want it to feel like an app, but I want to use plain JS; I want to leverage everything modern browsers can support, while remaining backward-compatible (!); I want to try odd things like using Lua inside nginx for everything (or even writing my own web server), or programmatically reorganizing my CSS and JS so runs of similar characters are grouped together and gzipping has the best effect. I also have a hazy idea of what I want the site to be about (not a content site, some sort of interactive thing) but I haven't resolved all the "but if you make it about X, it doesn't really nail all those bits about Y you wanted" stuff yet. Anyway.

Thanks for the note that AppCache is now out of the picture. I actually think I remember reading something vaguely about it being not the greatest, but I didn't know it was actively harmful. Do you mean in a security sense or it just being bad for performance?

I wasn't sure what to say about the content structure thing at first, but then I thought: take the pragmatic approach. Gather piles and piles and piles of actual content and dump it either on the site itself or your dev version. Notions about structure, presentation and content will likely occur in the process of accumulating (or writing) what's on the site.

As for what kind of content to put up, I would suggest focusing heavily on links to (and/or articles about) pragmatic, well-argued/well-reasoned arguments for lightening page load, and the various kinds of real-world metrics that are achieved when people make the investment to do that.

An obvious example: it's one thing to say "I recommend http://vanilla-js.com!", it's quite another to say "YouTube lightened their homepage weight from 1.5MB to 98KB and made it possible for brand new demographics in 3rd-world countries to experience video playback (http://blog.chriszacharias.com/page-weight-matters). Also, the reason the site feels so fast now when you click from one video to the next is that the platform only pulls in the new video URL, comments and description - the page itself never reloads."

Regarding where to start, I was thinking that a mashup/ripoff of halfway between https://developers.google.com/web/fundamentals/ and MDN might be an interesting target to aim for. I'm definitely not saying to [re-]do that much work (although I wouldn't be protesting if someone did... some of those Fundamentals tutorials are horribly out of date now), I'm just saying, the way that info is presented could do with cleanup and you can always run rings around them in various ways (layout, design, navigational hierarchy) because of bureaucracy blah blah... but you could do worse than aiming for something that feels like those sites do. Except you'd be focusing on making everything as lightweight as possible, and you would of course make the site your own as time went by. Maybe what I'm trying to get at here is that nobody's done a full-stack (as in, "bigger picture") top-to-bottom "here's how to do everything lightweight, and here are a bunch of real resources" sort of site yet, and I'm suggesting the lightweight-focused version of Google Web Fundamentals... :/

On a related note, I've come across a few websites that are nothing more than a bunch of links and a tiny bit of text describing some technical/development issue or whatever. They almost feel like spam sites, except they talk about legitimate issues and are clearly written by a person.

I'm sure these people mean well, but the low-text high-link format (or the "I'm going to rewrite what's in this link in my own words" approach) doesn't work for blog sites (possibly because of WordPress's 10000-clicks-to-get-a-high-level-overview browsing model...tsk) and similar - I'm trawling for actual text when I'm on a site like that, if you give me a link I'm not even on your website anymore.

You've probably seen sites like that too. (Note that I'm slightly griping here, I don't see your site as similar at all. I think I got a bit off track, I was trying to demonstrate the exact opposite of the direction I would suggest you go in. :P)

Also, I just thought of https://www.webpagetest.org and https://jsperf.com. Arguably microoptimization-focused, but I thought I'd mention them anyway.