What could it be? Your love and your time. There are a multitude of ways you can give of yourself without spending a dime.
Visit a friend. If you haven't seen them in a while, just the sight of your face will be a gift. Conversation with a friend is a priceless gift.
Stop by the home of an elderly friend and clean their baseboards. Sounds too simple, doesn't it? But think how difficult that one chore can be for someone getting up in years.
Babysit. A young family may not be able to afford a dinner out when you add the cost of a babysitter. Take away that cost and let them enjoy their evening. Or give a single mother the opportunity to do the grocery shopping without having to juggle the diaper bag, the car seat, and the groceries!
Girls' night in. Throw in a dvd and hit the couch with your girlfriends for a night of comedy or scare each other silly! You not only catch up on the latest flick...but on each other's lives.
A hug. Yes, a hug. The only gift guaranteed to double in value as soon as you share it. Those few seconds can make a significant difference in someone's day.
Just a few ideas...I'm sure you can come up with dozens more. Remember, the most precious gifts are those from your heart.