With the way the economy is today, everyone can appreciate the fact that money is tight. Even in online business. While paid ads will still net you a better profit, these free ad exchanges will get you started. I am proud to be able to present you with a couple of free ad exchanges. They are credit based. I would suggest opening a G-mail account, so the exchange ads don't clog up your personal email account.
As I try other free exchanges, I will pass them along.
To your success!