#1 Skill for successful community building: Hustle. If you can combine hustle (and bury any feelings of shyness) with some level of domain expertise, then you have a good chance of fanning an ember into a small flame. I've noticed this as I build and cultivate interest in UXForum.com. I relentlessly reach out directly to industry folks by email/skype/IM/phone/in-person to talk about what I'm building, how it will provide value to them and to generally sell them on the vision. You have to love doing it and you have to enjoy people.