There are deals this summer for travelers who know how to play their credit cards. Travel companies are offering promotions such as discounted rates, free gift cards, free rental days, free hotel nights and extra frequent-flier credits when you purchase travel.

Southwest is offering $25 off a future round-trip flight when you purchase a Southwest gift card of $100 or more. The card must be purchased online with a U.S.-issued Visa card by June 30. The $25 fare discount is valid for ticket purchases made between July 1 and Aug. 30, with a seven-day advance purchase, for travel Aug. 18 through Nov. 19. Travelers will receive the $25 airfare discount by e-mail. One fare discount per cardholder or e-mail address. Go to www.southwest.com /rapid_rewards/giftcard _visa.html.

Book a weekly rental with Avis with a MasterCard and get a free rental day at participating locations in the continental U.S. The offer is valid when renting intermediate through full-size four-door cars (Group C through Group E). The rental must be at least five consecutive days, with a Saturday night included, and must begin by Sept. 1. Use coupon TUPA008 when booking. Contact: 1-800- 331-1212; www.avis.com.

Guests at participating Marriott Hotels and Resorts will receive a $25 Visa gift card when they pay for their stay with a Visa card. The offer is valid on weekend and Stay for Breakfast rates for stays through Sept. 1 in the continental U.S. A Friday or Saturday night stay is required. The gift card is valid for use through Nov. 30. Use code V12 when booking. Restrictions apply. Contact: 1-877-627-7468; www.mar riott.com.

AirTran is offering extra A+ Rewards credits for each one-way flight you purchase with an American Express card. During this promotion, travelers will earn 1.5 credits one-way, instead of 1 credit, on coach-class flights in Y, B or M class, and 2.5 credits for any paid business-class flight, instead of 1.5 credits. Travelers can redeem eight credits for a one-way coach- class flight. The offer is valid for travel completed by Dec. 31. Go to www.airtran.com /american_express_rewards .aspx.

Tom Parsons is publisher of Bestfares.com.