Michael Phelps' dominance in the pool here in Beijing is causing a ripple effect throughout the collecting world. Given the lack of swimming memorabilia, compared to the traditional sports, collectors hoping to pick up Phelps items might have noticed a huge spike over the last couple of days.

"It's one of the most stunning developments the trading card world has seen in quite some time," said Tracy Hackler, associate publisher of Beckett.com.

While many items are now selling for hundreds of dollars apiece on eBay, Hackler has had his eye on Phelps' 2004 Leaf Rookies & Stars autographed card.

Ebay Phelps' 2004 Leaf Rookies & Stars autographed card

"The card was selling for as low as $30 a few weeks ago," Hackler said. "It's now trading online for between $400 and $500. We've raised the price almost $300 in the last two days and that number is sure to go higher.

Said Hackler: "Michael Phelps is the greatest American Olympian of all time and he's captivated seemingly everyone in the country, including more than his fair share of collectors, and new collectors."

Update: I just spoke to Phelps' agent Peter Carlisle about Phelps and a possible memorabilia deal. This is what he had to say: "We're currently receiving numerous offers from many of the leaders in the memorabilia industry. What has been most interesting is the extent to which the interest and offers have increased on a day-to-day basis as Michael has succeeded. We intend to consider all the options in the context of our overall plan and strategy and move forward accordingly."

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