Biodiesel.org - Retail Fueling Sites
This will help you find a bio retailer.

I use B50 to B80 during the winter depending on the temps. When I go to a real cold location I just use Dino Diesel with a little stanadyne. I generally don't like to run anything under B30 if I don't absoluttly need to. I don't think it is that great for seals and hoses in our truck. Biodiesel will swell them and ulsd will shrink them.
From mid April to the begining of October I run her on B100.