I saw your post and I may be able to point you in the right direction. A couple of questions:
1) Is your organization already registered on the Ariba Network?
2) If you are, are you currently receiving POs from a buyer using the Ariba Network?
If you answer to the above two questions is "no", then may I suggest you take a look at Ariba Discovery? http://discovery.ariba.com
Discovery is a solution where buyers post what they are looking to buy and their request get routed to sellers that match the particulars of the post.
If your answer is yes to either of the questions above, I would still encourage you to look at Discovery but you might be interested in packages to move your investment in the Ariba Network from a transaction solution to a sales and marketing platform. You can find more details here: http://www.ariba.com/solutions/b2becommerce.cfm and here http://www.ariba.com/solutions/connection.cfm
If you need me to put you in touch with one of our representatives to answer your questions in more detail, please let me know.
Ariba, Demand Generation