You can get $100 USD Facebook Advertising Credits coupon for free by just entering to http://apps.facebook.com/visabusiness and register for it. Note that it is no register fee.
Once you registered, Visa Business will send you a confirmation email to activate your Visa Business account. Then you can redeem your $100 Facebook coupon and 75$ Yahoo Coupon from them. It is free!
Before you redeem your coupon, you must make sure you owned a credit card. Because Facebook will ask you to key in your credit card or debit card information. But don’t worry, because Facebook will use up the free $100 credits, then only start charging from your credit card. If you don’t want Facebook charge from your credit card, you can stop advertising once it almost finishing your free $100 credits.
After you redeemed your Facebook Ads Credits Coupon, you must use it within 1 month. You can start advertise your stuff, your website and your Facebook Fans Page in Facebook right panel sidebar.