misterchimpy on Slickdeals describes the way to take advantage of 2 current offers by Hertz.
First, register for the Hertz Free Days promotion at
For every 2 day rental between 10/15/2013 and 12/15/2013, you will get 250 points (free weekend days start at 550 points) + 100 bonus points for an airport rental. Additionally, you will earn 50 bonus points for registering and another 50 for completing a short survey. So you can be almost 80% of the way to a free weekend day with just one discounted rental!
Now, make your weekend reservation for an economy or compact car with airport pickup through 1/31/2014: (it looks as if other class cars may be available at similar discounts).
It's a good deal – availability of the discount rental seems good too. Sign up for USAA membership (free) before your rental to claim the add. discount.
Hertz requires 600 Gold Points for a free rental – so two (2 day) airport rentals will get you there.