Ross, unless you are in the business of supplying business services/products to all other businesses, it might helpful if you could specify a vertical - in case anyone knows of any well qualified industry/vertical specific directories.
Does the mention of a "PPC component" indicate that your foremost concern is driving traffic - not simply "getting a link"?
Webwork: Yes - nearly any business would (and does) consume these products. It's difficult to answer both you and Centime in the same thread. I'm looking for links that provide relavancy in the eyes of the SEs, and/or a PPC platform to supplement campaigns with the SEs.
Centime: business.com provides decent traffic through PPC. Doesn't pay the rent but keeps the cleaning lady in vacuum bags. Lot's of bags :)