Other possibilities, not all necessarily 'rationalist':
http://www.acceleratingfuture.com/michael/blog/
http://felicifia.org/
http://www.utilitarian-essays.com/
http://naturalism.org/
http://www.infidels.org/
Most of those are in the queue now. (I think linkchecker crashed somewhere spidering the latter 5, so I'm not sure how complete coverage is.)
One of my long-standing interests is in writing content that will age gracefully, but as a child of the Internet, I am addicted to linking and linkrot is profoundly threatening to me, so another interest of mine is in archiving URLs; my current methodology is a combination of archiving my browsing in public archives like Internet Archive and locally, and proactively archiving entire sites. Anyway, sites I have previously archived in part or in total include:
Having recently added WikiWix to my archival bot, I was thinking of re-running various sites, and I'd like to know - what other LW-related websites are there that people would like to be able to access somewhere in 30 or 40 years?
(This is an important long-term issue, and I don't want to miss any important sites, so I am posting this as an Article rather than the usual Discussion. I already regret not archiving Robert Bradbury's full personal website - having only his Matrioshka Brains article - and do not wish to repeat the mistake.)