We signed up with American Airlines to get a group discount. This entitles you to a 5% discount on airline tickets and also car rental with Avis.
Message from AA.com:
The Discount Code you may give your guests is A4397AH.

Your guests will receive a 5% discount off the lowest applicable published air fare.

Discounts are valid 29Sep-13Oct, 2007 for travel to MIA – Miami, FL.

There will also be a separate ticketing charge of $10.00 USD for tickets purchased via the phone or $15.00 USD for tickets purchased at the airport. This amount is subject to change. At this time there is no ticketing fee for reservations made and ticketed on www.AA.com. The percentage discount can be booked on-line at www.AA.com for American Airlines and American Eagle flights only.

For your International originating guests, they will need to call their local reservations number and refer to your Discount Code (STARfile authorization number).

To receive the discount off Avis rental cars, please call 800-331-1600, and reference AWD - D003737.