Congratulations! You just won a $100 gift card!

That's what those emails and pop-up ads keep telling me, anyway.

Of course, I'd have to buy something (maybe several somethings) and jump through hoops (maybe several hoops) to get a "prize." And if I did that, then I'd get slammed by spam and/or telemarketing calls.

Scammers notwithstanding, it is possible to get gift cards for free -- sort of. Few things in life are truly free. You may have to click on an email, take a survey, utilize a specific search engine, attend a Twitter party, transfer a prescription, use a rewards credit card or maybe buy a few things you were going to buy anyway.

For the most part, you can get gift cards without spending a nickel. All it will cost you is time -- maybe a few minutes a day, maybe a little more.

Seriously: Would you really miss five minutes a day? Some people spend that much time staring into the closet and wondering what to wear. And if you're unemployed, on a tight budget or in debt, those few minutes could make a big difference.

Kymm S., an Iowa resident who asked that her full name not be used, spends about 15 minutes a day on MyPoints and Swagbucks. The two programs yielded her $200 worth of gift cards for the 2011 holidays -- a real boon in a lean year.

"I've been unemployed or partially employed for the past 17 months," she says, "and was very glad to have those (cards) available."

Even people whose books are currently balanced are aware that life can change without warning. That's why we're frugal. That's why we like free gift cards.

The old reliables

Start with established sites such as MyPoints, Swagbucks, QuickRewards and My Coke Rewards. But keep an eye out for new rewards programs. I just joined Superpoints, which is similar to the above-mentioned sites; it's invitation-only, but you can probably wangle an invite through its Facebook page.

A growing rewards trend is for e-coupon and location-based shopping apps like SavingStar and CheckPoints. Kenia Perales, a stay-at-home mom in Edinburg, Texas, earns points from seven such programs. They're easy once you get in the habit of using them, she says.

A bonus: "I let my children scan items at the grocery store for points, and that keeps them entertained."

Survey sites often give the option of gift cards versus cash. Do the math before committing, though. A company might require as many as 10,000 points for a $25 gift card -- pass! I once saw a site that let users trade points not for gift cards but for entries in gift-card sweepstakes. Riiiiight.

Tops among readers are PineCone Research, Toluna, Synovate, i-Say, Clear Voice Surveys and Valued Opinions.

How do you separate legitimate rewards websites from the scammers and spammers? Online user reviews are a good start. Or look for bloggers who recommend such sites. It's likely that they get fees for referrals, but a reputable blogger probably won't risk alienating readers forever to make one-time bucks.

'Splurge without guilt'

MyPoints is the granddaddy of the rewards programs, having been around for more than 15 years. Users can earn points in many ways, such as reading emails, buying things through the site (which has an affiliate relationship with many major retailers), playing online games and redeeming manufacturers' coupons.

Points can be cashed in for gift cards from dozens of merchants. Restaurant cards -- Applebee's, Panera Bread, Outback Steakhouse -- are quite popular, MyPoints President Matt Wisk says.