They're also opening early...
The stores are all closing at 6 tonight, so if you haven't shopped yet you're seriously running out of time. By all accounts this has not been a gangbuster Christmas shopping season for most retailers. So the push to get last-minute shoppers into the malls is really on. In addition to extended hours, stores are offering deep discounts.
Last-minute ideas: Gift certificates that you can print out from online retailers at home. Gift cards - some grocery stores and convenience stores have racks of them. Or a donation to charity in someone's honor.