If you're playing this game, pay particular attention to the specials on the alamo.com site. They have some good coupons right now (like free weekend day, $30 off a weekly rental, etc.) that Alamo doesn't always offer. They are fully combinable with the promo rates, including Alamo's "last minute" rates (which are useful for weekend rates, not so useful for weekly rates).
With these deals, I've now been able to drive down my daily car rental costs on a couple of rentals even further, to $11 to $13/day + tax/fee for a full size car. Priceline starts looking ridiculously expensive.
Oddly, Alamo's sister company, won't allow me to use coupons with their similar last minute rates (I would prefer to use my Emerald Club status to avoid the line). For 20 bucks, though, I'll wait on line.