The Work Better Weblog calls it your “back porch:”
Let’s say a business is a house, and the website is it’s front door - the formal method of greeting visitors - strangers or customers.
The blog then is the backporch. More informal. Probably can’t be seen from the street. Lots of voices and lots of conversations. A place where friends, customers, and colleagues all hangout together.
I’m using this the next time someone asks me why businesses need blogs. Read the rest of the post, there is lots more interesting stuff in there.