Actually, why aren't they here already?
I think that this is because they didn't intentionally come here. SIAI is a fairly popular cause around here because of how many people came to the site to read Eliezer Yudkowsky's writing. That group of people is largely sympathetic to SIAI, and hence SIAI is popular.
Edit: The following is very likely to be inaccurate, as its all based on first-glance impressions. I think that the structure of "people don't come unless they have reason to" applies though.
I don't think that any other groups have had that clear of an incentive to be here. GiveWell has their own blogs and other support areas, and though some of them may be interested in rationality, I don't think the particulars of how politics ruins your decision-making or how to dissolve questions appeals to or is that important to them.
I think the same is true of Wikimedia, where they already have some place to go and without any directed recruitment effort they wouldn't bother to come here as a group.
Every site linked to from Future of Humanity Institute seems like they could potentially be interested in things, but they all seem to have slightly different interests than rationality qua rationality. Quite a few of them (practical ethics, bioethics network) seem to have a philosophy bent, and I'd think that lack of using standard philosophy terms, or knowing standard philosophy arguments is probably hurting us with them.
We have a bunch of individuals with non-SIAI interests, but no causes other than SIAI, despite Eliezer repeatedly saying that they would be welcome.
I think that this might just be the non-SIAI individuals not intentionally trying to work with similarly interested people to advocate for their goals. I'm worried that something like that might get political though.
I think the same is true of Wikimedia, where they already have some place to go and without any directed recruitment effort they wouldn't bother to come here as a group.
Sue Gardner (exec director of WMF) plugged LW on her blog: Four essays every Wikimedian should read! (exclamation mark in original.)
This post is prompted by a short discussion with Wei Dai. He says:
Perhaps we should get other causes to participate/recruit on LW? Actually, why aren't they here already? We have a bunch of individuals with non-SIAI interests, but no causes other than SIAI, despite Eliezer repeatedly saying that they would be welcome.
He has a good point!
Here's my plug, for the cause I spend lots of my time and energy on, Wikimedia/Wikipedia:
Wikipedia/Wikimedia is more analogous to a software project than an ordinary charity - your money is useful and most welcomed, but the real contribution is your knowledge.
Or, more generally: create educational material under a free content licence. If it's CC-by-sa, CC-by or public domain, it can interbreed and propagate.
(Then we need to fix the things wrong with the editor experience on Wikipedia ... though the Wikimedia Foundation is paying serious attention to that as well of late. In the meantime, if you find Wikipedia too personally annoying to participate in directly, writing your own site and CC-by-sa'ing it still helps a lot.)
What good causes can you think of that are relevant to LessWrong and its community, that leverage effectiveness through rationality? (I'm thinking beyond just legally-blessed charities, right down to the "small circle of conspirators" level of trying together to get something done.) As well as SIAI, LW has previously had plugs for GiveWell. What do you spend your time, effort and/or money on?