Here's an interesting article from an old Harvard Business School Working Knowledge series. It's about branding, which from my perspective is a very diffucult thing to incorporate in online communications.
Websites and emails, for example, need to reflect some kind of graphical relationship with the rest of your organization. But I think they should also reflect a "tone" of your organization and its role in the world.
This article deals with these concerns in a broader sense. Here's a bit:
One of the additional challenges nonprofit brands face is that they must appeal to a broader array of stakeholders. Nonprofit brands have a dual objective: to enhance fundraising and to ensure the implementation of the organization's mission. In addition, nonprofit organizations tend to be more decentralized, with little formal hierarchy. This can mean that implementing activities that protect the brand or attempting to update or modify the brand often meets with resistance internally. In some cases, highly decentralized organizations such as Medecins Sans Frontiers [also known as Doctors without Borders] depend on their brand to provide organization cohesion. The brand is the glue holding the components of the global organization together.
You can read the whole thing here: HBS Working Knowledge: Social Enterprise: The Tricky Business of Nonprofit Brands