Rob Dyrdek, a 32-year-old professional skateboarder and MTV reality-show star, got a recent reminder of how low he is on the celebrity totem pole.

Last month Dyrdek, who stars in the show "Rob and Big," gave a friend permission to use his name to peddle Dyrdek's old car, a 2000 Mercedes-Benz CL500, on eBay. The highest bid: $29,600, nearly $9,000 below the Kelley Blue Book value. "I ain't Brad Pitt, and this ain't Donald Trump's CL," Dyrdek concedes. His friend, who now owns the car, plans to relist it in the next few weeks.

A few years ago, well-known celebrities began pitching their castoffs online for charity, generating big premiums and waves of publicity. In 2005, a pair of jeans owned by singer Britney Spears reportedly sold for over $4,000 on eBay.

It wasn't long before B-listers adopted the hot new method of self-promotion. In December actress Tori Spelling, best known for a television show that went off the air in 2000, garnered heavy press coverage when she held a yard sale, hawking everything from lip gloss to furniture.

Now, the traffic in famous people's used goods is dipping to new depths: a busy market in used cars supposedly owned by obscure celebrities. Some are so little-known that the sellers don't even seek a premium price, instead simply hoping that partaking of the American infatuation with celebrity any celebrity will help them move metal.

A recent search of sites like Autotrader.com and Craigslist turned up more than two dozen cars claiming celebrity pedigrees. Some recent opportunities: A Porsche 911T listed as actor David Hasselhoff's old ride, a 1989 Mercedes coupe advertised as once owned by Michael Bivins (of the 1990s group Bell Biv DeVoe), and a 1999 Chevrolet Tahoe SUV that is said to have been previously owned by an unnamed actor "who dated Whoopi Goldberg."

Rob Chesney, vice president of eBay Inc.'s eBay Motors division, says celebrity-car sales, while small, are a growing category for the Web site. Jennifer Kingsley, a full-time seller on eBay, says a recent listing for a car once owned by Jon Fishman, drummer of the rock band Phish, got over 2,000 hits, compared with about 30 hits for ordinary car listings Kingsley has handled in the past.

Unlike actual collectibles such as the late Pope John Paul II's 1975 Ford Escort (purchased when he was a cardinal), which sold for $680,000 last year, C-list cars frequently don't add much if anything to the sales price. The highest bid on a 2000 Chevrolet Corvette coupe reportedly owned by Brad Whitford, the guitarist for rock group Aerosmith, was $22,300, or $4,700 under the Kelley Blue Book retail price estimate.

The highest eBay bid Norman Kornitzer received for his 1983 Porsche 928, advertised as once owned by actor Stephen Baldwin, was $5,800. On eBay "I had a couple of people write sarcastic remarks like, 'Do you own a car owned by a more famous Baldwin brother?"' Kornitzer says. (Stephen, the youngest of the Baldwin brothers, appeared in the 1995 movie "The Usual Suspects.")

Last week, he sold the car through a local newspaper classified ad for $9,500, about twice its Kelley Blue Book estimated value. But Kornitzer says the buyer wanted this particular type of Porsche, not bragging rights to Baldwin. Baldwin's manager, Alex D'Andrea, declined to comment.

Like the used-car salesman in a famous "Seinfeld" episode who claimed a car was once owned by actor Jon Voight, when the owner actually was a periodontist with the same name sellers often base their car celebrity claims on title and other paperwork. Other ads are placed by individual owners who were told of their car's history by a salesman.

In many cases, there's little proof the celebrity ever owned the car in the first place. In December, Katie Heffelfinger of San Diego says she bought a 1990 Volkswagen Multivan for $8,600, in large part because the listing said it had once belonged to Michael Keaton. She's since nicknamed the van "The Batman," after Keaton's film role as Bruce Wayne. The price was on the low end of the vehicle's estimated Blue Book value.

Because photocopies of the car's previous title bear the name Michael Douglas Keaton's real name Heffelfinger says she believes "with 75 percent certainty" that it actually belonged to the actor. She also says she remembers seeing a television interview with Keaton in which he spoke of his interest in Volkswagens.

Last week, Heffelfinger sold Batman for $15,000. She says she got that price because of a healthy market of Vanagon enthusiasts and some repairs she had made, but she believes Keaton's name helped seal the deal. Keaton, through a representative, declined to comment.

Robin Arcuri, who has posed for Playboy, played a small part on HBO's "Entourage" and appeared in Mountain Dew ads, says she got several offers for the 2002 Mercedes CLK-430 she was selling on eBay last September, including one for $52,000, which was $12,000 more than she was expecting. She turned that offer down, in hopes of getting an even higher price. Now, nine months later, she says the car is worth less and she'll relist it again, but doesn't expect to beat her highest offer the first time around. The Kelley Blue Book value for the car is $27,920 in fair condition to $30,085 for good condition.

Arcuri did wonder whether bidders may have been hoping for more than just a car: "I think they're possibly just interested in meeting me in person."