A few more codes.

PC # 151653 - AAA members get two car class upgrades (I'd wager that you don't need to be using a AAA CDP to use this PC number, though)

PC # 151572 - $10 off per day on Weekly/Weekend rentals *at airport locations* up to $40 off in total.

PC # 151561 - one car class upgrade at HLE locations (zzzzzzzz)

The first two promotions are good to the end of January. The last snoozer is good until February 28th. Hope this helps someone!