I recall reading previously that Marriott Rewards is probably one of the better choices for frequent stay program credit associated with a Hertz rental at 500 points a pop. I've been going this route or choosing Southwest credits recently.

Do any of the airlines offer considerably more favorable mileage than others (without the requirement of a flight in conjunction with the rental)?

I'm on track to rent 40-50 times this year, and it would be neat if I could aim towards getting an award of some sort on a carrier I normally wouldn't fly.

Who knows, maybe the Icelandair 'Vildakort' program offers a Fedex reindeer steak pak for 10,000 kms or something...