If you have money and she loves coffee, a Starbucks gift card. Or a basket of her favorite snacks. Or a gift card for a manicure/pedicure. If you have no money, do some chores around the house for her. Give her a card that says "this is good for one weeks worth of dish washing or laundry, or whatever, and I'll do it all without a single complaint!". Believe me, moms appreciate all the help they can get around the house--especially if they work outside the home.