In this thread on creditboards.com there is a list of businesses that will give young businesses net-30 that report to D&B. Once you have 5 people that report to D&B/Experian saying you paid your bill, you are able to get some corporate credit cards, and its all uphill from there.

I have recently learned that business to business checks take forever to clear, so this stuff really matters as a buffer against that.

Instructions for establishing business credit once you get a DUNS, bank account, etc.