To start with, you can reach us on diaspora* at email@example.com. (That is not an email address, although it certainly looks like one. That's OKSocial HQ's diaspora* account; you can send a message to it after you sign up for an account of your own ...)
You can also reach your local administrator on any OKSocial diaspora* server as podmin.
If you're having trouble registering or logging in to an OKSocial server, please email us directly.
If our system is completely offline, we'll probably be very busy trying to bring it back. In that situation, you can reach us or get updates on Twitter @OKSocial_HQ. You might want to go ahead and follow that account, since in a catastrophic incident (like a PG&E planned outage, for example) this server will probably also be down ...
We do also have a facebook page, which we use mostly to run ads on facebook telling people that there are alternatives to facebook. It's not really a good way to contact us; frankly, it's more like performance art.