People talking to people
Ken points us to Emma. I have no idea if their email service is any good, I've never tested it. I can tell you that their site is really good. Great, even. It's written by real people to be read by real people. The tone is just right.
It's not the only way to design a b2b site. But it's sure a good way.
[Bryan would like you to compare that site to this one.]