An organization that has been displaying some activity lately is the Lifeboat Foundation. I've been asked to join their advisory board. My reply was yes, because I think it's a good cause, the niche was bound to be filled eventually, and I'd like to be involved. The main focus of the organization, which is currently run part-time by a single individual supported by dozens of big names, is to build a space ark as an insurance policy against global technological disaster. The idea is to start with an orbital space station, then create improved versions incrementally more distant from the source of potential trouble (orbiting the Earth, then the Moon, then Mars).
My perspective on the issue is that most disasters can be avoided by simply going underground in an isolated area. Going into space seems somewhat too excessive and expensive to be realistically attainable in the short term (5-10 years). However, the organization will sponsor research in self-sustaining habitats, a technology with useful applications for underground living as well. But if it's a disaster that a 5-stories-underground self-sustaining habitat in Antarctica can't handle, then I doubt a space ark will help much. The primary concerns:
Nuclear war: famous studies have shown that many millions would survive.
Killer virus: extremely unlikely to wipe out literally everyone.
Grey goo: this is an implausible risk, sensationalized by clueless journalists.
Nano-dictator: if they have nanotech and you don't, you're finished.
Unfriendly AI: there's nowhere to hide from a self-improving superintelligence.
How would an orbital lifeboat be useful? Perhaps in some kinds of nanotech arms races, or possibly other risks we haven't considered yet. Certain people will work towards self-sustaining space habitats no matter what, so they might as well be organized. The Lifeboat Foundation is a wise initiative in this direction.