Now that the season's holiday presents have been unwrapped, big online auction sites are trying to entice people to resell -- instead of return -- unwanted gifts.

Yahoo Inc. is preparing to open a section of its auction Web site specifically designed to help disappointed recipients resell gifts at no cost. Tuesday, Overstock.com Inc. started a promotional campaign encouraging shoppers to get rid of less-than-perfect presents. "Polyester sequined pants not your style?" asks one of its Web ads, which includes links to a guide on how first-time users can put items up for auction. EBay Inc. says it will promote online regifting through its Web site and Tuesday held a one-day promotion, cutting some listing fees to 10 cents.

The efforts are aimed at luring new customers at a time when they find themselves swimming in stuff they can't use. Unlike retailers for whom unwanted gifts often spell unwanted returns, online auction sites celebrate the objectionable necktie or the not-quite-right wallet as a potential gold mine of new listings and a convenient way to attract new customers to their sites.

When Bonnie Sarana received a brown Coach "hobo" handbag from her aunt this Christmas, she immediately thought of eBay. "I am just not a big fan of pocketbooks with logos," explains the 30-year-old from Brooklyn, N.Y. She says she would rather sell the item online than face the embarrassment of asking her aunt for a receipt. So she brought it to a local eBay drop shop -- where consumers can have their items put up for bid by a professional -- and has listed the item at a starting price of $9.99. She hopes it will sell for around $100, leaving her with a hefty amount even after the drop shop deducts its 30 percent fee.

Online auction sites usually notice a post-holiday rise in listings, but retailers predict that gift-reselling will increase even more this year as consumers face tighter return policies. Stores are cracking down on fraudulent returns by implementing stricter rules and, in some cases, by charging restocking fees that can be around 15 percent of the purchase price. Increased traffic across online auction sites in general, meanwhile, has online retailers expecting a particularly strong reselling season this year.

Deeper discounting later in the season also means that that sweater you would like to return is likely to fetch significantly less than the original price -- making reselling it all the more appealing. Today, a retailer may offer you only $30 for a sweater originally bought for $60. But online auction sites hold at least the potential of a better deal. Some products -- especially scarce items such as must-have handbags and electronics -- often sell for retail price or more. More conventional items, however, such as everyday clothing may still sell for much less than the retail price.

The extent of Internet reselling can't be precisely measured, of course, since it's not clear which postings are unwanted gifts. An eBay-commissioned survey conducted by Survey.com in November found that about 10 percent of respondents had sold unwanted gifts online. Among 25- to 34-year-olds, 22 percent of respondents said they had done so. And online retailers expect to feel the effects. Overstock.com says holiday-gift reselling is likely to drive the number of items posted by individual sellers on its auction site up by as much as 25 percent through January.

Analysts also say the Internet's role in decreasing the stigma often associated with reselling is likely to send more gift sellers online. Over the past few years, buying and selling used items online has become mainstream in part due to the anonymity behind the transaction. Online auction sites are among the fastest growing Web sites among users. EBay attracted more than 56 millions unique visitors in November, according to Nielsen/NetRatings, up 10 percent from a year ago.

The fact that it is getting cheaper and easier to post to online auction sites is also likely to fuel gift reselling. Online retailers say the prevalence of digital cameras and even camera phones will also help to increase listings as will the growth of drop shops where consumers can have their items put up for bid by a professional who typically takes a cut of around 30 percent of the selling price.

The steps required to auction off an item on the Internet can be straightforward. Sellers start by taking and uploading a picture of the item before entering a description and choosing the listing category. Sellers may be charged a listing fee anywhere from a few cents to a few dollars and be asked to turn over 5 percent or more of the selling price to the Web site. They must set the starting or asking price of the item as well as the duration of the auction and are notified of the winner when the auction has expired.

But closing a transaction is often not as easy as starting one. First-time sellers can be at a disadvantage when trying to unload their gifts since auction Web sites, particularly large one such as eBay and Overstock.com, are dominated by professional sellers with huge stocks of inventory and years of experience. To boost the chances that their regifted items will sell, users should accept PayPal to avoid fears of payment fraud and provide detailed product descriptions so that shoppers know exactly what they are getting, an eBay spokesman says.

Leah Jordan, 38 years old, says she is waiting to resell some gifts she received for Hanukkah until January when traffic on the Web rises as potential buyers return to work or school. But in past years she has resold several gifts, most often gift cards because they retain most of their value. Last year, Ms. Jordan, a lawyer in Philadelphia, says she sold a $50 Lands' End gift card for just over $40 and a Baby Bjorn gift card, worth about $95, for about $10 less than the retail price.

The reselling trend represents options not only for sellers, but for buyers too as thousands of new items flood the auction sites. Shoppers can hunt for recycled gifts by sorting items by the most recently listed and by searching for product descriptions that include the word "new." But shoppers looking for deals shouldn't expect to find hot items like iPods. Instead, they are likely to see lots of clothing, a difficult gifting category often plagued by sizing errors. Other popular items include gift cards, which sellers post for slightly less of their value, and knickknacks and collectibles for the home.