Both Facebook and Google are exploring the idea of portable community - which means that soon corporations and organizations will be able to create and embed applications and widgets from both community networks into their own websites.
Facebook's recent announcement (which is converted from very geeky tech-speak to real language beautifully by Jeremiah Owyang - a true industry guru - here) means that organizations will soon be able to move active Facebook onto the organization's main website more seamlessly.
Similarly, OpenSocial will allow anyone to build an application and embed it on any site that accepts OpenSocial (again elegantly converted from tech-speak to real language by Owyang here) meaning that organizations can build and then reuse the same elements over and over again in multiple settings.
Both of these developments are still very new and still need to be allowed to evolve further, but the idea of portability is what matters. Soon your organization's website - on it's own - will not be enough to spread your message or house your community of supporters. Start thinking now about how to create the kind of presence online that will allow users to interact with you wherever they are - and will allow them to act as evangelists for your organization within their own circle of friends.