It’s hard to imagine, but estimates are startling when it comes to cash left on the table in the form of unused gift cards this year. While we’re getting better at using every penny available on Aunt Edna’s Visa gift card, there’s still a lot of holiday loot that’s not bought every year via those convenient gift cards. In fact, this year, that number is expected to to hit the $1.7 billion mark.

Most of us will use it all; in fact, it’s estimated a full 75% of consumers will not leave a single dime on their gift cards. And a third of us will not only use our gift card, but we’ll kick in our own cash in the process too, at least $25, according to CEB surveys.

Here’s what many consumers don’t know, however. There are new rules, courtesy of the 2009 CARD act that puts into place compliance guidelines associated with expiration dates and burdensome fees.

The advisory company also forecasts 85% of Americans will give at least one gift card this holiday season, and we’ll spend close to $110 billion to do it. Here’s the interesting twist this year: we’ll spend $19 billion on restaurant gift cards.

This is considerably higher than previous years, partly because more restaurant chains are coming on board. Meanwhile, the traditional gift cards offered by the big credit card companies like American Express, Discover and Visa, will easily top $40 billion and store specific cards, like Wal Mart, Bass Pro Shops and Target, will total close to $37 billion.

Even digital gift cards, like those we buy at Amazon, have seen a big jump this year, the growth isn’t nearly as aggressive as the traditional gift cards, which is surprising because it was expected this particular gift card option would be the fastest growing for years to come.

The fact we’re spending more this year on gift cards could suggest the economy is on the mend. There have been many signs, including record breaking Black Friday, Cyber Monday and this week’s Free Shipping Monday – all of which have surpassed early expectations.

The lower drop in unemployment is another sign, too. Still, many are wondering whether or not finding a solution to the fiscal cliff before the holidays could have lent to even stronger sales.

At any rate, it’s believed the numbers will grow quickly each year with expectations by 2015 of more than 10% growth in some specific card areas.

Consumers like gift cards because it allows the recipient to choose exactly what he wants. It eliminates so many returns, too since the recipient is available to try clothes on or to choose the right color and brand.

It stands to reason it’s a fast growing sector. The variety of gift cards fuels the growth, too.

There’s another consideration, too. Often, we receive gift cards for stores we don’t shop at. Seems like a wasted effort until you consider the fast rise of swap sites that allow consumers to trade in those less than ideal gift cards for those they’re far more likely to actually use.

These sites have been popping up over the past few years and have filled a niche that would otherwise result in even more unused gift cards. Some sites even allow a trade in for cash.

But there’s a catch. Depending on the service the consumer uses as well as the popularity of the card, consumers might also receive only part of the face value of the card.

The sites are easy to use and require visitors to first create an account, which is always free, and then provide details of the card, such as merchant name, value and expiration date. Each site has different rules it plays by, but it all comes down to the same thing – it allows users to trade gift cards.

Each site, after keying in all of the information, will provide the user with the value or card redemption amount. Users then may choose to receive cash via PayPal or select a new gift card from the site.

Once the consumer’s unwanted gift card is mailed to the company, he sees either a new gift card or cash to his PayPal account – usually within two days.

There is a cost, though. While setting up the account is free, there are sites that charge additional fees, shipping costs and even service fees. Not only that, it can be easy to lose track of expiration dates and other restrictions on a gift card.

The sites are great for those wishing to not see a relative’s money go to waste, but like everything else in the credit sector, paying attention to the details in crucial. Some sites even allow users to donate their gift cards to charities.

How many gift cards do you typically receive this time of year? Do you trade them in or are you fortunate enough to receive the general purpose gift cards?