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Distributed Systems for Fun and Profit is pretty good: http://book.mixu.net/distsys/single-page.html.

Focuses on theory results that are applicable to real systems and analyzes those systems.

I haven't kept this up to date for a while now, but https://gist.github.com/macintux/6227368 may have some content of interest.

There is a distributed systems Slack group. Sign up here: https://dist-sys-slack.herokuapp.com/ There is a channel for links to papers.