Apart from just building a fantastic website and community (which you already seem to have done), what about advertising (responsibly, of course) on other websites? I'm not too sure what websites you would want to advertise on. Reddit maybe?

As for Server Fault, what if you tried to form some kind of 'partnership' (or agreement) with some hosting companies to provide a place for technical resources and other content that may be beneficial for their customers. Of course, the downside is that you do not want Server Fault to be seen at the support website for a particular web hosting company. What Slicehost did with Slicehost Articles is very good, and it could be used as a source of inspiration as to what to do.